I second the idea of implementing small utilities. It's also good when you're an experienced programmer and are learning a new language. OP, besides that I sug

I second the idea of implementing small utilities. It's also good when you're an experienced programmer and are learning a new language. OP, besides that I suggest you try and write a simple, text-based chat program before trying to write an IM. For instance, start with a 2-way chat, add error handling, then start adding support for multiple users, chat rooms and irc-like commands.