A sync station allows multiple windows mobile devices to connect to one PC without being prompted to setup a partnership. 

You can also edit the registry directly to enable Guest access for ALL devices. Modifying the registry can be dangerous, make a backup if you're not sure what you're doing! Use the "regedit" tool to add a new DWORD (32-bit) key to HKLM\Software\Microsoft\Windows CE Services and set its value to 1.

See:
http://support.microsoft.com/kb/270136

NOTE:
In Windows Vista and Windows 7, there is NO active sync. It’s called “Windows Mobile Device Center” (http://www.microsoft.com/windowsmobile/en-us/downloads/microsoft/device-center-download.mspx)

Therefore, this method will NOT work in Vista/7/2008 server