I'm using a sweex LC100060 802.11g usb card with slackware 10...works fine, though I needed to add two lines to my rc.local file to get it to load automatically at start up. No big deal. The chipset is a Ralink 2570 (though it says 2500, but the radio controller is 2570) and I'm using the open-source driver from http://rt2x00.serialmonkey.com/
(the 2570 driver, not the 2x00 or other drivers). Hope that helps.