If you happen to come across a smart phone such as the currently hyped iPhone which can connect to the Internet via GPRS/EDGE and wonder how to configure it for the US based T-Mobile network then these basics should get you going:

In case you have T-Zones use:
APN: wap.voicestream.com

In case you have T-Mobile Internet use:
APN: internet2.voicestream.com

If this doesn’t work (e.g. because you have a FlexPay account) or you have VPN use:
APN: internet3.voicestream.com

You should be able to leave the username and password empty. If you experience issues try “guest” and “guest” as username and password.