I've been using Novatel's Merlin XU870 broadband card for a year or two now with my AT&T Wireless account, and have loved it (though I do wish it were a little faster).
But I just saw Novatel's new Linux-based MiFi product, and I'll admit I'm drooling at the prospects.
Basically, it's a portable 3G broadband wireless modem/router...one that can fit in the palm of your hand. Roughly the size of a credit card, the worst thing about the MiFi is that my odds of losing it are pretty high.
The Novatel MiFi is set to start shipping in early 2009. Too bad I can't get it as a stocking stuffer.