Freenet, is a free software, that allows you publish and obtain information on the Internet without fear of censorship by means of a decentralized, anonymous network, with built-in support for downloading and uploading large files. It divides all files into 32KB blocks (called CHKs), which’re each fetched and decrypted separately. Freenet uses a lot of memory, takes a long time to complete the startup process, and crashes if you queue too many downloads. By storing the current progress of uploads and downloads in db4o.com's open source object database (= a file on disk) rather than in memory, Freenet's memory usage can be greatly reduced, the end-user doesn't need to worry about running out of memory, we can have an unlimited number of uploads and tens of gigs of downloads, and so on.

More info: Google Open Source blog