Check out Pro Chaps...
By far the best half chap I've ever owned/ridden in (yes, I've been notorious to hop on friend's horses at times and must have chaps ;)). They also make full chaps and western chaps... but really, check them out. I love them and they are in the same price range as some of the other chaps listed. They are calfskin leather too! So soft... and conform to your leg. Honestly sometimes they don't even feel like they are there. They are made to pretty much fit everyone, I am a really hard fit because I have weird (tiny) ankles and a decent sized calf so... I really love them. I've had mine for almost 2 years and I am sad to say I don't take great care of them but they are holding up great. When it comes time to replace them I will DEFINITELY be getting another pair. Everyone I know who has a pair of Pro Chaps has no complaints ;)
... on another note, I've heard good things about Tredsteps.