Sam Gentile points to the latest version of Lutz Roeder's Reflector, version 4.0, which supports all versions of .NET Framework, inckuding .NET Compact Framework and future releases like 2.0 (Whidbey) and 1.5 (Longhorn preview).
I have the chance to put my hands on a brand new AMD64 powered Compaq laptop, running a beta version of Windows XP 64-Bits Edition, on which I installed a beta of Yukon 64-Bits for AMD64 and also a .NET Framework 2.0 for AMD64, taking advantage of it's 64 Bits processor.
I tryed to run Reflector 4.0 in the CLR64, but for some weird reasons, it refused to launch, even afterI provided a .config file - I have to dig out to understand what happens. Anyway, a simple ILDASM /OUT and ILASM did the trick and now I confirm that Reflector 4.0 also runs in 64 Bits .NET Framework ;-)