Check out Dave "Pragmatic" Thomas's blog entry Kata14 where you'll be challenged to generate sensical text by using "trigrams"...

I've tried his solution, and with a varied enough text base to feed it, it generates some impressive texts with so little effort... I guess you can improve it to check longer strings as well, but you'd end up with a Markov Chain (de|re)generator, which could be interesting on itself, but...

(suggestion: the Gutenberg Project is a great place to get good base texts for feeding the database :-)

Link: PragDave's Kata Fourteen

Good luck,