An Introduction to Formal Languages and Automata eBook

That book doesn’t contain pure algorithms theory (like Kormen’s or Skiena’s book), but problems (and most of them are with solutions). Every chapter starts with the simple problem, followed by some discussions of possible solutions, and after more and more challenging tasks ends with pretty tricky problems.
The book (in my opinion) is really very practical (well, it contains some theory, but not very formal) and is invaluable for those who are preparing to the programming contests or Google/Microsoft-like interviews.