I'm taking from Jaki's list in his (original) centenary retrospect, so it only goes up to the mid-eighties. What are the Gifford Lectures? They are an endowed lectureship at four Scottish universites on metaphysics, natural religion, and the foundations of ethics, and arguably the most prestigious academic lectureship in the English-speaking world. The lectures are presented for the purpose of eventually being published, although not all lecturers have actually done so. Published lectures I have read are bolded.
Edinburgh
1888-1890 J. H. Stirling, Philosophy and Theology
1890-1892 G. G. Stokes, Natural Theology
1892-1893 O. Pfleiderer, Philosophy and Development of Religion
1894-1896 A. C. Fraser, Philosophy of Theism
1896-1898 C. P. Tiele, Elements of the Science of Religion
1900-1902 W. James, The Varieties of Religious Experience
1903-1904 H. M. Gwatkin, The Knowledge of God and Its Historical Development
1905-1906 S. S. Laurie, On God and Man
1909-1910 W. W. Fowler, The Religious Experience of the Roman People
1910-1912 B. Bosanquet, The Principle of Individuality and Value ; The Value and Destiny of the Individual
1913-1914 H. Bergson
1915-1916 W. M. Ramsay, Asianic Elements in Greek Civilization
1919-1921 G. F. Stout, Mind and Matter, God and Nature
1921-1923 A. Pringle-Pattison, The Idea of God in the Light of Recent Philosophy ; The Idea of Immortality
1926-1927 A. S. Eddington, The Nature of the Physical World
1927-1928 A. N. Whitehead, Process and Reality
1928-1929 J. Dewey, The Quest for Certainty
1930-1931 N. Soderblom, The Living God
1932-1934 E. R. Bevan, Symbolism and Belief ; Holy Images
1934-1935 A. Schweitzer
1937-1938 C. S. Sherrington, Man on His Nature
1938-1940 R. Niebuhr, The Nature and Destiny of Man
1940-1941 O. Kraus
1947-1949 C. Dawson, Religion and Culture ; Religion and the Rise of Western Culture
1949-1950 N. Bohr
1950-1952 C. E. Raven, Natural Religion and Christian Theology
1952-1953 A. J. Toynbee, An Historian's Approach to Religion
1954-1955 R. Bultmann, History and Eschatology
1956-1957 A. Farrer, The Freedom of Will
1957-1959 W. Kohler
1959-1960 R. D. Maclennan
1961-1962 J. Baillie, The Sense of the Presence of God
1962-1964 D. Daube
1964-1966 D. M. Mackinnon
1966-1968 H. D. Lewis, The Elusive Mind ; The Elusive Self ; Freedom and Alienation
1968-1970 W. H. F. Barnes
1970-1971 E. L. Mascall, The Openness of Being
1971-1973 PANEL (A. Kenny, H. C. Longuet-Higgins, and C. H. Waddington) The Nature of Mind ; The Development of Mind
1973-1974 O. Chadwick, The Secularization of the European Mind
1974-1976 S. L. Jaki, The Road of Science and the Ways to God
1976-1977 J. P. Jossua, Pierre Bayle ou l'obsession du mal
1977-1979 J. C. Eccles, The Human Mystery ; The Human Psyche
1979-1980 N. R. Smart, Beyond Ideology
1980-1981 S. H. Nasr, Knowledge and the Sacred
1981-1982 I. Murdoch, Metaphysics as a Guide to Morals
1982-1983 D. Daiches, God and the Poets
1983-1984 M. A. Arbib and M. Hesse (Jaki doesn't have the title, and I don't remember it, but I've read it)
Glasgow
1888-1892 F. M. Muller, Natural Religion ; Physical Religion ; Anthropological Religion ; Theosophy or Psychological Religion
1892-1894 W. Wallace, Lectures and Essays
1894-1896 J. Caird, The Fundamental Ideas of Christianity
1897-1898 A. B. Bruce, The Providential Order of the World ; The Moral Order of the World
1900-1902 E. Caird, The Evolution of Religion ; The Evolution of Theology
1903-1905 E. Boutroux, Science and Religion in Contemporary Philosophy
1907-1908 A. C. Bradley, Ideals of Religion
1910-1912 J. Watson, The Interpretation of Religious Experience
1913-1915 A. J. Balfour, Theism and Humanism
1916-1918 S. Alexander, Space, Time and Deity
1919-1921 H. Jones, A Faith that Enquires
1922-1923 A. J. Balfour, Theism and Thought
1923-1925 W. P. Paterson, The Nature of Religion
1927-1928 J. S. HAldane, The Sciences and Philosophy
1929-1931 J. A. Smith
1932-1933 W. Temple, Nature, Man and God
1935-1937 W. M. Dixon, The Human Situation
1937-1938 W. E. Hocking
1938-1940 J. Laird, Theism and Cosmology ; Mind and Deity
1946-1948 R. B. Perry, Realms of Value
1949-1950 H. H. Farmer, Revelation and Religion ; Reconciliation and Religion
1952-1954 J. Macmurray, The Self as Agent ; Persons in Relations
1955-1956 L. Hodgson, For Faith and Freedom
1959-1961 C. F. Wiezsacker, The Relevance of Science
1962-1963 C. W. Hendel
1965-1967 H. Butterfield
1971-1972 R. W. Southern
1974-1975 B. G. Mitchell, Morality, Religious and Secular
1979-1980 S. Brenner
1981-1982 S. Clark, From Athens to Jerusalem
1981-1982 C. J. Larner, The Thinking Peasant
1982-1983 A. J. Sanford, Models, Mind and Man
1982-1983 P. Drew
1983-1984 A. D. Galloway
St. Andrews
1888-1890 A Lang, The Making of Religion
1890-1891 E. Caird
1894-1896 L. Campbell, Religion in Greek Literature
1899-1901 R. A. Lanciani, New Tales of Old Rome
1902-1904 R. B. Haldane, The Pathway to Reality
1907-1909 J. Ward, The Realm of Ends
1911-1913 J. G. Frazer, The Belief in Immortality and the Worship of the Dead
1914-1916 J. A. Thomson, The System of Animate Nature
1917-1919 W. R. Inge, The Philosophy of Plotinus
1919-1920 L. R. Farnell, Greek Hero Cults and Ideas of Immortality
1926-1928 A. E. Taylor, The Faith of a Moralist
1929-1930 C. Gore, The Philosophy of the Good Life
1932-1933 R. R. Marett, Faith, Hope and Charity in Primitive Religion ; Sacraments of Simple Folk
1935-1936 H. H. Henson, Christian Morality
1936-1937 W. Jaeger, The Theology of the Early Greek Philosophers
1937-1938 W. G. De Burgh, From Morality to Religion
1938-1939 J. Bidez, Eos
1939-1940 R. Kroner, The Primacy of Faith
1946-1948 E. Brunner, Christianity and Civilization
1948-1949 A. M. Macbeath, Experiments in Living
1951-1953 B. Blanshard, Reason and Goodness ; Reason and Belief
1953-1955 C. A. Campbell, On Selfhood and Godhood
1955-1956 W. C. Heisenberg, Physics and Philosophy
1956-1958 V. A. Demant
1958-1960 G. H. von Wright, Norm and Action
1960-1962 S. Runciman, The Church in Captivity
1962-1963 H. Chadwick
1964-1966 J. N. Findlay, The Discipline of the Cave ; The Transcendence of the Cave
1967-1969 R. C. Zaehner, Concordant Discord
1970-1971 W. H. Thorpe, Animal Nature and Human Nature
1972-1973 A. J. Ayer, The Central Questions of Philosophy
1975-1976 R. Hooykaas, (Jaki doesn't have a title, but it has since been published, its title is something about the development of science and I've read it)
1977-1978 D. Stafford-Clark
1980-1981 G. Vlastos
1982-1983 D. G. Charlton
1983-1984 J. Macquarrie, In Search of Deity
Aberdeen
1889-1891 E. B. Tylor
1891-1892 A. M. Fairbarin, The Philosophy of the Christian Religion
1896-1898 J. Ward, Naturalism and Agnosticism
1898-1900 J. Royce, The World and the Individual
1900-1902 A. H. Sayce, The Religions of Ancient Egypt and Babylonia
1905-1906 J. Adam, The Religious Teachers of Greece
1907-1909 H. Driesch, The Science and Philosophy of Organism
1909-1910 W. Ridgeway
1911-1913 A. Pringle-Pattison
1913-1915 W. R. Sorley, Moral Values and the Idea of God
1917-1919 C. C. Webb, God and Personality ; Divine Personality and Human Life
1921-1922 E. W. Hobson, The Domain of Natural Science
1924-1926 W. Mitchell, The Place of Minds in the World
1927-1929 E. W. Barnes, Scientific Theory and Religion
1930-1932 E. Gilson, The Spirit of Medieval Philosophy
1935-1936 W. D. Ross, Foundations of Ethics
1936-1938 K. Barth, The Knowledge of God and the Service of God according to the Teaching of the Reformation
1938/39, 1946/47 A. D. Nock
1947-1948 J. Wisdom
1948-1950 G. Marcel, The Mystery of Being
1951-1952 M. Polanyi, Personal Knowledge
1952-1954 P. Tillich, Systematic Theology
1956-1958 H. A. Hodges
1960-1962 H. H. Price, Belief
1963-1965 A. C. Hardy, The Living Stream ; The Divine Flame
1965-1966 R. Aron
1966-1968 T. M. Knox, Action ; Layman's Quest
1969-1970 A. T. van Leeuwen, Critique of Heaven ; Critique of Earth
1972-1974 H. Arendt, The Life of the Mind
1975-1977 J. Z. Young, Programs of the Brain
1979-1980 F. C. Copleston, Religion and the One
1981-1983 A. Hultkrantz
1983-1984 R. Swinburne, The Evolution of the Soul
They are very much a mixed bag, although they tend to be good. Some of the better ones, in no particular order: Gilson, Marcel, Price, Driesch, Heisenberg, Thorpe, James, Lewis, Jaki, Daiches. Some of the worst, IMHO: Ayer, Toynbee, Hobson, Blanshard, Dewey. Bohr's lectures were apparently so bad he went from a lecture hall of hundreds to less than ten stubborn advanced physics students; and they all remembered the lectures as monotonous to the point of horror. Some of the Gifford Lecturers since Jaki's list peters out that I can remember off the top of my head include Onora O'Neill, Carl Sagan, Richard Dawkins, Michael Ignatieff, Charles Taylor, Richard Sorabji, Martha Nussbaum, Eleonore Stump, and John Haldane.
(UPDATE 11/22/04: I've made a few minor corrections - one (Driesch) was accidentally left without bolding, and another (Smart) was accidentally bolded that shouldn't have been. At least I don't think it should have been; I've read a few things by Smart, but I don't think I've read the work in question. As you might expect, given the vivid impression Smart's works have left on me, I'm not in a hurry to read it, if I haven't already. I thought of another important recent Gifford Lecturer, Stanley Hauerwas, With the Grain of the Universe, which I have read. The Hooykaas book, now that I think of it, was called something like Faith, Fact, and Fiction.)
