Free Internet connection speed and bandwidth test

My favorite is at SpeakEasy.com. You can find it at http://www.speakeasy.net/speedtest. It's Flash-based, so you need to have Flash installed for it to work. You have different options of where to test the connection to, but they're limited to the United States.

If you're from outside the US, another option is http://www.speedtest.net/. It lets you pick from several different locations around the world to test your connection, so you can find one close to where you will be downloading/uploading to. I actually just found this one, and after looking at it, it may be my new favorite.

Here are some others:
http://www.bandwidthplace.com/
http://reviews.cnet.com/internet-speed-test/
http://www.auditmypc.com/internet-speed-test.asp
http://performance.toast.net/