Ryan Hall Triangle
Ryan Hall is one of the best instructors in the world - this is a 3 DVD set in which he covers everything you need to know about triangles: from the correct finishing position to set ups from every angle. If you check it out on amazon.com or budovideos you'll see it's not cheap - but it's well worth it.
I'm selling for £39 (which is a lot cheaper than you'll get it anywhere else!) It's in perfect condition - I've watched it a few times and learned a lot from it.
Oh - there are clips on youtube if you want to see a clip.