Speedtest is a nifty little bandwidth tester that gives you some indication of the capability of your connection -- as tested from various servers around the world.  My office pays for 4Mbps service and the tests I did got 3.731Mbps from Los Angeles, 3.851Mbps from Chicago and 1.329Mbps from London.  The latency for the Chicago test averaged 54 milliseconds, Los ANgeles 111ms, and London 143 ms.  Upload rates clock in at about 320Kbps.