+1  A: 

Beta 1 doesn't seem to support this yet. Its easily possible by using the new Taskbar APIs and specifically the custom categories feature. I think their main problem might be that the solution files are associated with an app called VSLauncher.exe (this small app determines what version of VS to load when you launch a SLN file).

If you want to "pin" your fav solution files to any version of VS, one option this is (I currently used this with VS 2008 and 2010 Beta 1:

  1. Open Explorer and browse to any SLN file you want to pin.
  2. Drag it and pin on the taskbar (it will pin to VSLauncher.exe; this is okay)
  3. Now just repeat the steps for other SLN files.

When you click on a SLN file from the above pinned program's jumplist, another instance of VS2010/VS2008 will launch. It won't show your recent projects or solutions, but atleast it allows you to pin your fav/recent solutions manually. I think you can use this for CSProj or other project files as well.

Keeron
+1  A: 

It is possible to pin solution files to the recently used file list.

  1. First make sure you already have Visual Studio pinned to the Start Menu.
  2. Next, drag the Solution file on to the Start Menu so that it is pinned in the main list.
  3. Now select the the Recently Used Files button for Visual Studio so that the list is showing.
  4. Drag the solution file from the main list into the recently used file list.
  5. You can now remove the solution file from the main list.
Nicholas