How small/light do you want? How much power do you need? What kind of quality/price range are you after?
I have an Atomic CLR that I love. But, it's kind of big/heavy and EXTREMELY loud. I wouldn't want to use it at a small coffeehouse/bar (background music) gig.
Alesis/Headrush/AltoTS/etc (lots of brands using the same speaker and slapping their name/brand on it) make great small/light ones. The 8" ones are very small and light, and can get quite loud. I think
@Chito used one to tour with for a while.