Android: If you take a lot of pictures on your phone and don't want to manually drag them onto your computer, DropSnap will automatically upload any photo you take to Dropbox, so they're ready for you when you get home.
Plugging your phone in to sync photos is a pain. DropSnap monitors a folder on your phone's SD card, so whenever you take a picture with your phone (or a screenshot of your phone), it'll automatically send it to your Dropbox folder, ready for access wherever you go. It's like Eye-Fi for your phone, but better, since it doesn't need to be anywhere near your computer to upload your photos.
DropSnap is a free download, but requires a $US3.99 in-app purchase for automatic uploading to work. If you stay with the free version, you'll get a notification every time you take a picture, which will let you enter the app and manually sync your photos. Check out the video to see it in action. And, if you're an iOS user, be sure to check out previously mentioned CameraSync, which does the same thing.