I've got a Delta Universal rack on my Muirwoods 29er.



You can get it from REI for $19.93 right now.

I've never really had any affection for this rack. I treat it like a red-headed step child, but I've been using it for three years and it's still doing the job it's made to do. I've thought about replacing it with something spiffier, but it's really hard to find a rack that will work with disc brakes AND fit over my 700x50 tires with room to spare for a fender.