Clean Up Your Android Device With SDMaid

"It's helpful to have access to your phone's SD storage, but it's concerning when you don't know what's a crucial data file and what's leftover cruft. SD Maid scours your SD card and clears out thumbnails, log files, and other stuff you don't need."

I've been using this for about a week now and it does what it says. You won't regain a lot of space, but every little bit counts and keeping caches clean can often keep your device humming along quite nicely. SD Maid is free for the downloading in the Market and works wherever the little green guy is rooted.