Try Nanette Blanchard's blog, Knitting in Color. Here's her first entry on Fair Isle, here's the second entry. Those will give you background and history.
Then you'll want to check out her tutorials on stranded knitting depending on how many colors you're using and how you want to hold them. Do check out Nanette's intarsia tutorials, as the techniques cross over quite a bit. (The link there is to my blog, where I have all three intarsia tutorials directly linked, sorry, too lazy to do them again here!)
Lucy Neatby also gives some intarsia hints on her website.
Oh, and here's another way to hide ends when you're doing a lot of colorwork.
And don't forget the TechKnitter's tips and tricks too...here's multi-color knitting, one color at a time, with links to her other tutorials, too.
P.S. Can you tell I like learning from multiple sources?