I’m a HUGE fan of www.performbetter.com mainly because they have an excellent selection of fitness “props” and they continue to add new items to their inventory on a regular basis. Also, they usually have some sort of promotion running on their site that can save you money on shipping or on the overall price of your order.
IDEA World Convention will get you new equipment, at some great prices. I’ve snagged some kettlebells and a Bosu Ballast Ball there(which I wish I would have bought a few). But, if you really look, depending on where you live, Craigslist has TONS of value. I basically built most of my gym through Craigslist. I got Reebok Core boards for 15 bucks, a Free Motion Chest Press, which I use for EVERYTHING it seems like, for $600. Brand New, that thing is like four grand. Anyway. I think shopping around is the best way to go. There isn’t a one stop shop if you are trying to save money.
I agree with Leah…IDEA World! It’s one of the best opportunities to get all your equipment as well as to try them out at fabulous discounts!
I also use Fundamental Fitness Productss (www.funfitpro.com), Perform Better, Power System.