ScottGu announced VS 2005 HotFix Patch that speed up debugging ASP.NET related projects in VS 2005. You can read more about it in this KB article here.
Background on the Issue
The particular bug fixed in this hotfix was surprisingly difficult to track down. The slowdown issue occurred when breakpoints were set in multiple source files in the same project that had the same short file names (for example: two default.aspx.cs files) and which were organized in a certain directory structure pattern on disk. The patch fixes this issue and should prevent the debugger from pausing when trying to load the web project's assembly symbols in this case.