If you want to play Irish jigs and reals using a five string banjo and three finger picking, there's a superb instruction book by a guy called Tom Hanway, who's from New Mexico. He came to the Yorkshire Dales Bluegrass Festival in 1999 and astonished everyone with his technique. He told me that he is half Native American and went to New York to get work as a bluegrass player but could only get jobs in Irish bars, so he learned a lot of the tunes and developed his technique - he's very knowledgeable about them, and has spent time in the auld sod getting to grips with them.
He even played me some Welsh tunes (I'm Welsh) which he did beautifully, though I had to teach him how to pronounce the titles!
He's well worth looking into.
Cheers
Ray