I have had a lot of different flashes over the years. SB24's, SB28's, SB600's,SB700's, SB800's, and a few third party flashes now like several YN568EX's and i just recently got a Neewer 750II, as derrel linked my review. (braineack did a much more in-depth review though, but I think we basically came to the same conclusion)
I got the Yongnuo 568EX flashes because I wanted a few extra flashes with TTL and HSS. I sold my sb24's, sb28's, and sb600's a while back. (I hated the sb600 menu) the newest yongnuo flashes are the 568EX line and are $180 new. I found that they stack up very nicely against the SB700. I reviewed the 568EX flash
HERE. More recently, I decided to try out the newest of the Neewer flashes just as a spare off camera flash. the Neewer 750II was $60 brand new. I dont think it is quite as good as the sb700 or yn568EX flash, and it doesnt do HSS like the other two do, but for a third of the price of a 568EX I think its a great flash.
if you want TTL and HSS, i would recommend the yongnuo 568EX.
I think there is an older yongnuo model that does TTL as well.
if you dont care about HSS but still want TTL, the Neewer 750II is a great flash for the money.