Sharepoint v3 and MOSS 2007 offers a built-in support for mobile devices by using the so called "mobile views", a feature that permits to a mobile user (Pocket PC or Smartphone for example) to connect to a Sharepoint page and interact with its data. Obviously, don't expect to have the great Sharepoint/MOSS interface on the mobile device... the mobile view is only an HTML view of the Sharepoint site, but it does the work quite good. 
To enable the mobile view feature, you've to run this command on the Sharepoint/MOSS server:
stsadm -o activatefeature -name MobilityRedirect -URL http://yourSiteURL ,
where yourSiteURL is the URL address of your Sharepoint site.
Now you're ready to go mobile, simply by browsing the url http://yourSiteURL/m with your Pocket...
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Sharepoint