This is very cool. If you want to play with topic modeling I'd suggest starting with Mallet (http://mallet.cs.umass.edu) For an idea of what topic modeling can do, check out http://bit.ly/wikitopics which provides a web-based UI for browsing through Wikileaks' Cablegate dump (powered by topic modeling/LDA/Mallet).
Vowpal Wabbit (one of the fastest learning implementations, from John Langford, also of Yahoo!) now has an "online" LDA implementation (Hoffman et al 2010: http://www.cs.princeton.edu/~blei/papers/HoffmanBleiBach2010...). It's probably the fastest single-core LDA implementation.
