I have an external unlocked 3G modem board that works great with 2.6.24. Found it on ebay for $25. I think it counts as a mini-pci express bridge because the mini-pci express cellular modem it takes appears as though it would on a laptop.

Normally those cell modems show up as two usb serial ports accepting AT commands. One is for communication, and the other one is so you can query modem status information (signal, etc)

Although the E220 has been configured for Linux, I can't say for sure that it's because of the support of Huawei.

Vodaphone paid for and open-sourced research for Linux drivers for their HSDPA, so you might consider the Vodaphone:
[url]http://www.betavine.net/bvportal/resources/datacards[/url]
From [url]linux-drivers.org[/url]:

is a software suite for the mobile 3G datacard which works on multiple distributions of the Linux Operating System. Besides managing connections with different technologies like GPRS, UMTS, and HSDPA, this application supports receiving and sending SMS, access to contacts and offers diagnostic information for troubleshooting. The application is free to download and distribute. The software is open sourced technology from a project initiated by Vodafone Group R&D.