Came across this website, really useful, lots of mainly old folk tunes.
Chiff and fipple forums is a great resource and a very extensive and helpful forum. Everyone who penny whistles should belong to it, no matter what type of music they like!
The only word of caution I can think of is that they don't seem to have much patience for fun back and forth banter from beginners. Well then... maybe that's what THIS pennywhistleclub.com social site might be better for!