Ben Ryan - MSFT
Just out of curiousity are you running VS 2005 with or without SP1 There were a number of fixes that went into SP1 related to preventing the automatic addition of DLLs in the web project's Bin directory. I'm not sure if these fixes extended to automatic checkout scenarios.
Do the DLLs need to be checked into source control If not, you may be able to delete them from TFS and undo the pending adds, if VS tries to add them back.
If they do need to be in source control, then the following can be tried:
1) Install SP1 if it is not already present
2) undo the pending checkouts
3) Go to the Team Explorer toolwindow, right click the TFS server node, go to Team Foundation Server Settings->Source Control File Types and enable File Merging for Executable Files (e.g. .exe, .dll, etc.). This will cause the auto-checkout of the DLLs to be non-exclusive.
For further information see:
http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=1513714&SiteID=1
http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=742975&SiteID=1
--Ben Ryan