Lua Lanes is a pretty awesome solution for multi-threading (with OS threads) in Lua which uses message passing instead of shared data. LuaThread is the shared data alternative which we have considered for inclusion into LÖVE before, but it requires a custom Lua build and is no longer maintained according to Diego Nehab (which by the way is the creator of LuaSocket). I added experimental support for Lua Lanes into LÖVE yesterday (I was immediately convinced of its potential), as it seems by far the best available solution for multi-threading.
BitOp provides bitwise functions (as previously requested by some users). This library is quite new, and it's the first bitwise operations library which appeals to me. I haven't included it yet, but I will if people are still interested. By the way: BitOp is created by the author of LuaJIT.
Also, if you want to see a Lua library in LÖVE, please do suggest it, though I can't promise to include everything.