Just got my official (public) notification today, had to pass it along!  .NET CF SP3 and ActiveSync 3.8 are now available.

The CF.NET SP3 release notes are found on its page.  ActiveSync’s, though, are not listed there.  I’ve heard the only real changes were:

• Windows XP SP2 security pop up warnings that appear the
  first time a Windows Mobile devices is docked have been eliminated
• Remote PC Sync (via Wifi or LAN) is turned off by default.
  However, users can turn this functionality back on.

So if that’s all, not that critical of an update unless affected by these issues.  Be sure to check any installed readme files, etc. for more info.