On the .NetUserGroup Compact Framework mailing list, Derek Ekins asked about syncing work. At work we currently use a pull method, but are moving to a background thread pull method.
Nic Wise pointed out a MSDN paper I’d read a while back, about differed response HTTP messages as a push mechanism. This seems quite a clever method.
We also use a really great piece of software MobiControl by Soti Inc, that sends hello’s to the sever so the server can do true push, but this requires public IP addresses.