Does Speedtest.net not do this for you? There is the small problem that the local Speedtest.net server was moved from a high-quality independent ISP to Comcast, so all Comcast speed tests are now completely unrealistic.
Ookla — the folks who run speedtest.net — have interesting displays of the data they've collected:
Top download speeds by country:
I'm on sonic.net and get 20mbps down, 2 mbps up. You need bonded Fusion service to get those sorts of speeds though.
dslreports.com has speedtest results, down to zip code, though they don't include things like what service product and/or whether the service has some bandwidth cap.
edit: Someone should create a website that both tests your speed, but then also shares that result with the world (anonymously). I'd love to pop up a list of ISPs in a specific city and see exactly how accurate their listed speeds are before buying.