I think reading & interpreting results from academic papers and posting 'distilled' versions to a blog would actually be pretty good, especially since I'd (hopefully) get some constructive criticism out of it as well.
I can second this. When I learn about new topics I like to blog about them (betterexplained.com) to help cement what I've learned, and have a way to relearn (in my own words) a topic once I've inevitably forgotten. I think you'll find this rewarding for yourself and others.
How about doing a reading course with a professor-friend of yours?