What makes SD Maid so much better than all the other SD card cleaners available for the Streak is the sheer amount of things this one app can do. SD Maid is a complete file manager and a file searching utility, as well as an easy-to-use program for wiping out various temporary files and other extras that Android has left behind. The app also contains a few other goodies, such as a list of the top 50 biggest files on your SD card, for even more space optimizations.
There's also a pro upgrade available for purchase in the Market that adds in a few extra features.
Links: Market (Streak) | Market (web)