Android: Syncly keeps watch over your Android's SD card, automatically uploading new photos to Dropbox as soon as you take them -- so you don't need to do anything to keep everything synced to the cloud. We've talked about how to roll your own instant photo upload for Android before, and while apps like DropSnap are great, Syncly puts them all to shame.
All you do is start up the app, create an account, link it to your Dropbox and start snapping photos. Syncly will upload photos instantly after you take them, over 3G of Wi-Fi (whichever you prefer), silently in the background. No other app works that well or does it all for free.
Its only downside is that you need to create a Syncly account, which seemingly serves no purpose whatsoever. Even though it's quick, there's absolutely no reason you should have to do this; it should just be a simple Dropbox-linking affair. But, it is what it is, and the ease of the app is well worth the annoyance. Hit the link to check it out.
Syncly is a free download for Android devices.