For a definitive view of piobaireachd:

www.piobaireachd.co.uk

The Piobaireachd Society website.

It has some editorial content (the FAQ page is good), photos, and, perhaps most importantly, audio of some of the 20th century's greatest performers that you can stream.

If you're a piper, then you need to get a teacher to show you the basics (at least). If you're not a piper, then figuring it out by ear is probably the best bet, because many tunes are notoriously poorly notated.