Canon's 220EX has been out for ages to represent the "tiny little flash" market. The only problem is, it has no useful features to speak of that the built-in flash already has, just a smidge more power. It has no bounce or zoom, for example. The 270EX zooms and tilts up for zoom and even lets you control the advanced features on most of the modern G-series and EOS-series cameras via the rear LCD.

Sounds cool, but it's a little expensive, given the flash power.