Here at OStatic, we concentrate on open source applications, issues, and the business of open source, but freeware and truly useful free services are always on my radar even if they're not from the open source world. One example of a free service that will probably appeal to open sourcers as well as non-open sourcers is ADrive, which will give anyone 50GB of free online storage--far more than existing providers of free online storage, such as XDrive, are doling out.
I've followed the free online storage arena for some time now. XDrive has gotten a lot of attention for offering 5GB of free online storage. Then there are interesting players who don't offer all that much storage capacity, but serve up useful, free applications along with the storage capacity. Among those, Box.net is a very interesting example. It gives you access to a slew of free collaboration applications in addition to storage, though it only gives you a paltry 1GB of capacity. Across all the free storage services I've seen, ADrive looks to be delivering the most capacity.
With ADrive, you can upload files, download them, organize them in folders, and share links to stored online content with others. For remote workers, say, putting an open source application together, 50GB should often be enough to get meaningful work done without hurling huge e-mails back-and-forth or bothering with FTP applications.
If you haven't looked into this service, do so. That's especially true if you collaborate with others online.
Do you know of any useful, free services the open source community might like to know about?