The language (variants of interpreters and compilers) has changed so much over the years, the code might not work for you. I am preparing a port to some standard like R6RS, and hopefully the future R7RS, but this might take a while. Maybe in early 2013 I will have some of that ready for publication.

Natural Language Toolkit (SNLTK) homepage not up, use GitHub repo.
There is a new GitHub repo for the code: SNLTK

The SNLTK consists of libraries and tools for text and natural language processing. It can be used with Racket and other R6RS compatible Scheme interpreters or compilers.
Among others, you will find tools and algorithms for various purposes in the SNLTK:

ESSLLI (University of Malaga)

IPA transcription of Croatian text (web service, will be set up locally)