Dropbox now offers a free iPhone app. Not only can you manage your Dropbox files, but you can view any compatible file on your iPhone and even store "favorite" files locally, right on the phone, for fast offline access.
This is even cooler than it sounds. You can take advantage of Dropbox to access photos, video, and music on your iPhone, and you can share content with others by sending an email from the app (which includes a link directly to the file).
There's no charge for the app, but stepping up from the free service to 50GB costs $9.95/month. You can also get 100GB for $19.99/month.
If you're new to the magic of Dropbox, be sure to check out three cool ways to use Dropbox.