Buy the Red Dragon which can be obtained at fatbrain and PM gets a cut too.

It is an excellent introduction into grammers lexing, parsing, regexes, finite automata. Hmm, to be honest IMO it is one of the most interesting and generally informative comp sci books I have read. Definately worth the money to buy and read. And yes I know you said online material, but I seriously doubt you will find anything online that is of as high a quality and usefulness as this book.

Update
Doh! Mirod already suggested this and I didnt even notice. Well, two recommendations for a book this good is probably not such a bad thing.

Yves / DeMerphq
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