I'm working on a distributed / fault tolerant network filesystem inspired by plan9's Venti. Several of its internals (code for chunking data with rolling hashes, a purely functional ADT for non-redundant storing of large strings, and a coroutining / non-blocking server framework for Lua, somewhat like Python's Twisted and Ruby's EventMachine) have been broken out into their own libraries. I'm almost done with the first two and am working on the third, but its design is being driven by the filesystem. They'll all be released at once when they're done, no time frame yet though. Probably MIT license.

I've also been working an a utility to locate repeated groups of data (particularly geared towards scanning for likely copy-and-pasted code), but that's been put on the back burner due to the above project and lack of free time.