I bought a very inexpensive ($150) system from Behringer that I absolutely love for small venues like local dive bars with a small crowd. It is the EUROLIVE B205D Active 150-Watt PA/Monitor Speaker System and it mounts on your mic stand. Has two inputs that each accept XLR or 1/4" plug. It has input for your mp3 player, phantom power and a basic EQ.

It certainly won't compare with Mac's Bose L1 but it sounds pretty sweet for small venues and you can't beat the price!

And I just noticed they are replacing the 205 with a 207 which has a bit larger speaker, an additional mic input and a built-in mp3 player so you can play your recordings from a USB stick.