OpenNETCF have a free community edition of their extension library:
http://www.opennetcf.com/Home/tabid/36/Default.aspx
(among other things, contains a useful FileSystemWatcher which is missing from CF 2.0 SP2)
This Microsoft site has a few great tip and tricks:
http://msdn2.microsoft.com/en-us/netframework/bb495180.aspx
.NET Compact Framework Team
http://blogs.msdn.com/netcfteam/
Chris Tacke’s SDF Samples
http://blog.opennetcf.org/ctacke/CategoryView,category,SDF%20Samples.aspx
Neil Cowburn’s blog:
http://blog.opennetcf.com/ncowburn/
Jim Wilson’s Blog
http://www.pluralsight.com/blogs/jimw/
Peter Foot’s Blog:
http://www.peterfoot.net/CategoryView,category,NETCF.aspx
Mike Hall’s Blog:
http://blogs.msdn.com/mikehall/
Also, Issue 14 of the Architecture Journal has a mobile device focus:
http://www.msarchitecturejournal.com/pdf/Journal14.pdf