Dial-up, while an "older" technology is still effective at connecting a device to the internet or other network from just about anywhere.  The Compact Flash format has been around for years and comes in two physical sizes.  Type I cards are smaller, while Type II are slightly larger.  Quotes are from the respective companies webpage and are not a value judgment of davespda.com.
 

Ambicom CF56M-EZ - Check Prices
    "AmbiCom's EzJack Dongle-Free CompactFlash Modem Card allows you to have simple and direct access to corporate network, e-mail and the Internet without worrying about breaking or losing cables." - www.ambicom.com

Hawking HCF690V - Check Prices
    "A new generation of Pocket PC and CF+ Modem solutions is now giving dynamic, mobile workforces the freedom to be productive from any location." - www.hawkingtech.com

HP FA132A - Check Prices

Pharos PFM-C56 - Check Prices

Targus PA560U - Check Prices

Trendware TFM-CF56 - Check Prices

Feel free to email me about your own PDA, questions, comments, articles, rumors, and reviews.  I can be reached at dave@davespda.com.