There's one thing I've always wanted to do on my iPhone, but couldn't: easily create and manage photo albums on the device without having to sync with the desktop. I wanted to be able to split photos in different albums, say one for wallpapers and one for my dog's pictures.
The tweak's really simple: it puts a + sign in the Photos app, which allows you to create albums and password-protected albums. Once you create an album, you'll just have to select photos from the Camera Roll and move them to the new album. That's it. You can then move photos out of albums and back to the camera roll, and even delete albums with an usual swipe.
PhotoAlbums+ doesn't have any issues with apps that access the camera roll and syncs just fine with iTunes. Highly recommended. $2.99 in the Cydia Store.