TRENDware's TRENDnet TFM-CF56 is a 56K Fax Modem card in CompactFlash format. You can use it on devices running WinCE 2.0 or higher...either HPCs or PocketPCs. Sorry, but no support for PalmOS users. The modem supports the V.90 and K56Flex standards and can be used for data or fax.
It worked well in my tests, connecting to my dialup ISP at about 48kbps or so, after I figured out that my phone cord wasn't making contact with the CF56's connector contacts. The ability of the modem to switch to terminal mode either before or after connecting was helpful in debugging this problem. I was able to see the conversation between the modem and Casio E-125 PocketPC, which indicated that no dialtone was being detected. This debugging feature is essential, since there are no indicator LEDs on the device, nor is there the ability to listen to the modem connection sequence on the PocketPC's speaker.
No drivers are included with the CF56, since it works just fine with the drivers included in the WinCE/PocketPC OS. The printed manual covered the basics of installation, setup of POP3 mail, and using ActiveSync via a modem.