This gym bag from Gaiam is called Everything Fits ($60) because, well, you can pretty much fit everything in it! Forget having a bag to hold your workout clothes and towel and then a separate strap or bag to hold your yoga mat, this bag holds it all and then some.
The main interior compartment is perfect for your clothes, while the zippered pocket and elastic pocket can hold your wallet, keys, and cell phone for easy access. The vented outside pocket is designed for your shoes, socks, or a wet towel, and the side pocket is great for holding a water bottle.
And last but not least, keep your beloved yoga mat nice and secure with the adjustable straps located at the bottom!