I agree that Sharon Bogan's site, inaminuteago, is one of the best ones out there if you're looking for good stitch instructions. Besides her stitch dictionary, check out her crazy quilting displays and her examples of her own work: http://inaminuteago.com/
- that's the link again.
I also like http://www.needlecrafter.com
- there are some really nice patterns on there.
Needlenthread is pretty good - the explanations are good, I think, anyway, and it focuses mostly on basic stitches so you don't have run through the ones that might be more complex than you're looking for: http://www.needlenthread.com
They also have some good book recommendations on there for stitch dictionaries and such.
Speaking of the split stitch - how do you all do it???! I swear, all the diagrams show it being split from behind - coming up behind the thread on the fabric. I'm sure there's a reason for that, but I find it a lot easier going down from the top. Just my opinion....