I learned a long time ago that there was a way to disable the Windows shell extension that puts a pretty but often annoying face over C:\windows\assembly\. It's nice to be able to drag assemblies to it or do a right-click/delete, but it's irritating not to be able to treat it like a regular folder when you want to.
The standard way to disable the facade is to flip a bit in the registry: in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Fusion, set "DisableCacheViewer" to dword:00000010. You can flip it back to all zeroes if you want to turn it back on.
I happened to be doing a bit of digging to find this information again for the 20th time and found the first comment on this blog post here, which says that if you type C:\windows\assembly\gac into the Run box, it will disable the shell extension for that Explorer window and let you move around the GAC folders. Very nice. It works with other sub-folders of assembly as well, so you can browse straight to gac_msil if you like. It also works from the Win7 start menu smart-search text box, but it won't work if you type it into an Explorer path bar.
The standard warning applies: don't move stuff around in the GAC or add or delete things manually. The standard explorer view is best for being able to quickly copy assemblies out.