i use Speakeasy.net
. it's an online bandWIDTH (i notice for some reason you're saying bandwidge) tester. it's pretty accurate and easy to use
as a note, if you're on DSL, or cable broadband there are factors that go into the actual bandwidth you get compared to what you're paying for.
for DSL your distance from the ISP is a HUGE factor. if you live 2 blocks from the distribution center, then you'll get the advertised bandwidth almost 100% of the time. However if you live 30 miles away, you might reach the advertised bandwidth 50% or less of the time.
both cable and DSL are SHARED services. which means that EVERYONE in your area who's connected to the service is using the same "pipe" (wire, cable, etc..) so their traffic will slow your traffic down. so if you work the night shift, you'd probably notice that during the day when everyone else is at work you'd get really high speeds (possibly even OVER the advertised rate) but when everyone came home for lunch your speed would drop drastically because everyone's going to youtube or facespace or whatever.