I've just released on the Market my new ROM Updater!
Differently from koush's ROM Manager, this one is stand-alone repository based, it's freeware and ad-free. It can be easily integrated in your own ROM and it allows you to download full or incremental (if available) updates.
Besides updating your system, it allows you to automatically perform some recovery actions, such as cache/data wipe and backup just clicking on a menu item.
Comments, ideas and donations are welcome
Read more on my website: http://www.elegosproject.org/android-rom-updater