I’ve just found an excellent ReSharper plugin called Scout. This lovely little beast will open Reflector when you choose Go to Declaration. The thing I really love is that Scout also takes care of loading the appropriate assembly in Reflector. I previously had to load the assembly in Reflector before I could browse it, which took time. Scout makes this process seamless.
All you have to do is right click and select Go to Declaration:
Then you get taken to the item in Reflector and the correct assembly is loaded: