Hmm, if you stumble across it let me know. If you've build some secondary app that people are using you can probably get away with scraping out bits of the graph along the way, but most of the ones I've seen just do some very simple counting of friends rather than trying to do anything like finding clusters or trying to figure out which of them you're not likely to already know about.
Hey, I'm one of the guys who built WhoShouldiFollow. Glad the recommendations are working out for you.
The Twitter API rate-limiting makes things harder, but as a whitelisted app we haven't (yet) run into any situations where we've hit our quota or get throttled in any way.
