Developer, Former MVP, now at Microsoft - Best of 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013
Developers of Windows Mobile 6.x (and indeed Windows CE) applications still use the rich .NET Compact Framework 3.5 with Visual Studio 2008 for development. That is still a great platform and the Mobile Development Handbook is still a useful resource (if I may say so myself :-).
The release of Windows Phone 7, changes the programming paradigm. The programming model has NETCF in its guts, but the developer uses the Silverlight or XNA APIs (and they can call from one into the other). I thought I'd gather here (for your reference and mine) the top 10 resources for getting started.
If after all that you get your hands dirty and still can't find the answer ask questions at the WP7 development MSDN Forum.
On a personal note, I was pleased to see that the Parallel Stacks debugger window works fine with the WP7 project ;-)