Optech is kind of the standard for neoprene straps. I have a couple of them, and the quick-detach mechanism is handy for when you want to take the strap off.
I have heard good things about the Crumpler Industry Disgrace as well.
Blackrapid/etc. are some interesting designs if you want some "alternative" straps for carrying your camera in a different way than just around your neck, switching from one carry method to another quickly, etc. But the Optech and Crumpler are pretty much standard neck straps, just upgraded. From Optech, I prefer the "Utility Strap" design over the straight straps.
Keep in mind though, a thicker/padded strap will take up considerably more room in your bag. Depending on the size and configuration of your bag, this might be a nuisance. I usually keep my 5D in a Think Tank Digital Holster 20 (which has a snug fit around the camera), and I really have to fold up my Optech Utility Strap to cram it in there.