This application enables you to construct context free grammars and graphically step through a bottom up or top down chart parse of sentences of your choosing.
Documentation is available directly.
This application attempts to measure the entropy of English text through a method devised by C.E. Shannon. Documentation is available directly. Info Professor Eric Brill's home page . I believe this site maintained by Yahoo is comprehensive but here is a list of other archives . Here is another list generated by InfoSeek.