I just recently picked up a 6 shelf economy rack (white) from Animal Plastics. I love this particular rack because it was pretty economical - like $225 with belly heat (3" flexwatt)
http://www.animalplastics.com/1754EP.htm

You have to assemble it, but it's real easy. They have the groove cut in the shelves to keep the flexwatt lower than the tub. My favorite part about this rack, though, is that you can use both 15qt tubs as well as 32 qt sterelite tubs. I have both adults and juveniles in the same rack. It's really nice. I will have to get another 41 quart rack for the females as they get up to breeding size, but for now, they are all fitting well.

I like a lot of the homemade racks and may venture to build one at some point, but this AP rack is serving me very well for now.

God luck!