Okay, this is a bit slow and requires a lot of processing power and data downloading, but its quite useful if you are not in a rush, as well. As the networks in North America progress to faster bandwidths, I see this as being useful in the future - but not now, unless you have no issues with patience (I think most people with BlackBerry devices lack this virtue, however).
OTA Download: http://www.sreid.org/gmapviewer.jad
It may or may not work for your device. It does work for the 7100t, though.
Mark, I think you may take a liking for this, although its nothing like it is on the PC.