Dropbox has a lot of things going for it, but if you use the cloud storage service with any regularity, there's a good chance you'll bang up against the 2GB offered in the free version fairly quickly. (Assuming that you don't Gmail account chain trick outlined in our Dropbox Cheat Sheet, that is.) If you're chafing at your no-cost bonds, the service is giving you an opportunity to add up to another 5GB of space absolutely free -- if you're willing to be a guinea pig, that is.
Dropbox is still working out kinks in its as-yet-unreleased automatic photo and video upload support, you see. As this forum post outlines, if you download the experimental beta build (links found in aforementioned post), Dropbox will toss another 500MB of space your way the very first time you automatically upload a photo or video. After that, you'll get another 500MB of free storage space for every additional 500MB worth of photos/videos you upload. There's a 4.5GB cap on that, though, not counting the 500MB awarded for your original upload. Plenty of other tweaks and new features are also included in the build. (Thanks to Engadget for pointing the offer out.)
Dropbox also offers an Android version of the beta build, complete with all the same abilities and offers. It's not up in Android Market -- being a Beta build and all -- but you can nab the .apk file with this link that comes courtesy of Pocket Lint.