I turned mine into a retro gaming console. Got it working, fired it up, and realized that the games of yesteryear are are terrible compared to what's out there now (IMHO) and it's been sitting since.
My next idea is to run DNS and a web server on it. I'd like to set it up to just get DNS from Google and OpenDNS for most queries, but for known ad servers, to redirect those queries to a local webserver and have it set up to just return a 1x1 pixel transparent GIF to any and all requests. I'm thinking of doing it mainly just as an exercise, and partly to see how the sites that pop a "You're using an ad-blocker!" react to that.