I wrote this little reg file because I was tired of navigating to folders to open them.
Gone are the days of having to go through all the work (tongue in cheek) of opening Unity, navigating to a folder. Now with this registry file, you simply right click on a folder and Open in Unity. If you are using a prior version of Unity (4 or prior) note that your folder will be c:\program files(x86) not c:\program files.
Download this and save it as UnityRightClick.reg (I'll typically save it into notepad and rename the text document). To import it into your registry double click on the file. Note that if you are using Windows and don't have it setup to view your file extensions, you may be trying to execute a text file, not a registry file. Ensure your file ends in .reg and not .txt so Windows will iport this into your registry.
BTW if you are using Unity on Windows (as 88% of people do!) ensure you check out the FREE Visual Studio Tools for Unity