Computer tools can be used to assist research and teaching in the Humanities generally, and not just in Philosophy. In some cases, this simply provides ways of making existing methods of study more efficient, for example through use of text processing systems and searchable texts etc. Amongst the most important of these tools are the many Textual and Bibliographic Databases that are now available, which can make the discovery and accessing of relevant texts - both primary and secondary - so easy as to transform research that involves textual scholarship.
Even more exciting - though far less familiar - is the way in which computers can open the door to new methods of investigation, for example computational textual analysis, as supported by the Signature system for stylometric analysis which is hosted by this website. This software has been used to investigate such matters as the textual affinities between the books of the Bible, Plato's dialogues or Shakespeare's plays, the provenance of the various sections of Aristotle's Ethics, and the authorship of disputed texts such as the Federalist Papers. Recently, Signature has been used by scholars in the USA to identify Coleridge as the author of an 1821 translation of Goethe's Faustus (in an edition published by OUP in 2007). It also played a role in a dramatic claim by Republicans, just prior to the 2008 US election, that Barack Obama's book Dreams from my Father had been ghost-written by an ex-terrorist!
All of the Humanities can benefit from systems that display, process, catalogue, search and analyse texts, but the computer also offers some distinctive tools for philosophers, of which the best-known are probably automated logic proof systems. The range of these distinctive systems has grown enormously in recent years, as discussed in the page on this website devoted to Miscellaneous Electronic Resources.
For a few selected Web links and books concerned with Humanities computing, with a particular focus on those of most relevance to Philosophy, see References on Humanities Computing.