The AirCard 875 is a PCMCIA card developed by Sierra Wireless. It has a fixed antenna (this is the bit that sticks out of the side of your computer). The AirCard 875 supports theoretical data rates up to 3.6 Mbps on HSDPA networks. There is the possibility (via future firmware upgrades) that this card can provide peak data rates of up to 7.2 Mbps.

Reception can be improved in remote locations by the use of a secondary antenna. The AirCard 875 provides worldwide roaming with tri-band HSDPA/UMTS and quad-band Class 12 EDGE/GPRS connectivity. Supports HSDPA and UMTS on the 2100, 1900, 850 Mhz band. This is important since Europe uses 2100 mhz and North America uses 1900 mhz for HSDPA.

What to ask for:
First - The card you get must be UNLOCKED!
Second - The card can be "branded" (Cingular, ATT, etc.) or not

Where to get the 875 Aircard:
Ebay - (where I bought mine)
Sierra Wireless Store
AT&T
Ebay- Click Here For Unlocked Air Cards

Again... Just be sure (really really sure) that the device is unlocked if you are going to be using this outside of your network.

Supported operating systems:
Windows® Vista, XP, 2000, OSX

Misc:

Since I use an Apple laptop, I downloaded the free Sierra Wireless Watcher client (click on the OSX link to get it). They support Mac 10.4+.

I also experimented with nova media's most excellent piece of software "launch2net". This was very easy to use and could be used with a wide variety of other GSM devices. A feature that is nice, is the ability to measure both your upload and download traffic. This helps you know where you are in the scheme of where you are in terms of your billing from what ever provider you are using.

For best Aircard deals on ebay USA see seller sunsunsun they carry The Unlocked Sierra 875 875U GT MAX expresscard GT MAX 3.6 & more