Somewhat oddly (given the focus of the language and the fact that I'm doing Physics) I haven't spent much time on the numerical side. Partly that's because there's plenty of people doing that already, and I think Julia has a lot of potential as a general purpose language as long as the libraries (like Lazy.jl) are there.
My main projects for the foreseeable future are Jewel and perhaps a Markdown parser (which is Jewel-related). So what kinds of things are you interested in using it for, then?