Today is the feast of St. Anselm, so here are some resources relevant to the day. Online resources on Anselm are very uneven, but I've provided ones that I thought were at least interesting.
The best translations of Anselm's works into English that are online (indeed, that exist) are probably those of Jasper Hopkins.
On the so-called ontological argument, Hopkins's article Anselm's Debate with Gaunilo (PDF) is an excellent guide to some of the misunderstandings of the argument that need to be avoided. Gyula Klima's papers, St. Anselm's Proof and On whether id quo nihil maius cogitari potest is in the understanding, are probably the most interesting discussions that argue that the argument is sound. For interesting discussions that come to the conclusion that the argument fails, I recommend Peter Millican's The One Fatal Flaw in Anselm's Argument (PDF) and Peter King's Anselm's Intentional Argument (PDF). One of the fascinating things about Anselm's argument is that while very few people accept the argument as sound, almost no one agrees about why it is not. The two discussions, in King and in Millican, provide the most serious arguments I've found for the existence flaws in the argument. (My own view of the argument is similar to Klima's: it is sound but probably begs the question.)
On Anselm's vies about the Incarnation (and atonement, which is a major focus of Anselm's theory of the Incarnation), I recommend Nicholas Cohen's Feudal Imagery or Christian Tradition? (PDF), which points out a number of problems with the old canard that Anselm's model of atonement is 'feudal'. See also Michael Deem's discussion of Anselm's Chalcedonianism in A Christological Renaissance (PDF).
Katherin Rogers has an interesting paper on Anselm on Grace and Free Will (PDF). Hopkins also has a paper, Freedom of Will (PDF), that makes some interesting comparisons between Anselm and Harry Frankfurt on this subject.
Thomas Williams and Sarah Visser discuss the De Veritate in Anselm on Truth (PDF).
Jeffrey Brower discusses Anselm on Ethics (PDF).
Susan Krantz Gabriel discusses Brentano's Account of Anselm's Proof of Immortality in Monologion 68-69 (PDF).
John Janaro's Saint Anselm and the Development of the Doctrine of the Immaculate Conception (PDF) discusses Anselm's view on original sin. See also Kevin McMahon's Anselm and the Guilt of Adam (PDF).
A number of the above articles can be found in the excellent (and wholly online) Saint Anselm Journal.