DSL Reports speed test for iPhone is nice
Bandwidth checking for 3G devices is always informative as keeping up with your speeds is helpful. Most speed tests are not very optimized for mobile devices and if they are can be spartan to the point of boring. DSL Reports has long provided free speed tests and they have recently optimized a page for the iPhone which makes it fun to use. Worth a bookmark for sure, even saved to the home page.
@ home in Oklahoma City
1797kbps WiFi
497kbps 3G
4531kbps WiFi
1067kbps 3G (three seperate tests to verify)!
161kbps Edge