I know people that have a homebox and swear by it.

Buy-The-Homebox

Personally, it looks like the HTG Supply tent is a good one. I don't use a grow tent, but I've bought lights and equipment from them in the past and they have good stuff and good prices. Here's an example of their 4' x 4' tent

4x4-HYDROPONIC-GROW-TENT

which looks pretty handy for under $250, delivered.