There are a few popular (and extremely cool!) server components from Windows CE 5.0 that you can download and install on Windows Mobile 5.0: the Web Server, UPnP Device, UPnP Control Point, MSMQ and the PNRP service.
Since a large number of CE OS components are not shipped in Windows Mobile due to RAM and ROM constraints, I know several people have worked to get the web server running on Windows Mobile (PocketPC and Smartphone) devices in the past. You'll be happy to know that these are the same OS features you know and love just on the Windows Mobile devices. And you'll probably be even happier to know that you can download and redistribute them from this site: http://www.microsoft.com/downloads/details.aspx?FamilyID=cdfd2bb2-fa13-4062-b8d1-4406ccddb5fd&DisplayLang=en