I ran a feedreader at http://readwarp.com for 3 years, but haven't kept it up lately. It had a feed crawler using Python but the rest was in Arc. The codebase is at http://github.com/akkartik/readwarp. (I gradually got into improving the Arc stack rather than that particular app atop it, leading to my next couple of projects: http://github.com/akkartik/wart and http://github.com/akkartik/mu. Both are heavily inspired by Arc.)