Yes you can now run them as servers :) Richard Jones (UK Developer of the Year) has posted a 3-part article about how he took an old Compact IPAQ (H3600) and turned it into a Caller ID notification server using some clever hacks, hardware and custom software.

  

here are the links to his articles:

Old Pocket PC's make great servers

Old Pocket PC's make great Servers Part 2

Old Pocket PC's make great Servers Part 3

 

You only can do something this complex that easily using Microsoft tools. Go drop him a mail (richard_AT_NOSPAM_binaryrefinery.com) if you want the source. Yes he's giving it away! (being the nice guy he is) :)