By now, I am sure everyone knows that .Net Reflector is no longer freely available. Because of this, the SharpDevelop team has taken it upon themselves to cook up an open source alternative ILSpy.
I have been using ILSpy for the past couple of weeks. It doesn’t have the same plugin system and some of the reflected code looks still has a lot of IL looking code in it (goto statements, etc.), but for such a new tool, it works tremendously.
So, if you are looking for an alternative to .Net Reflector, I would recommend ILSpy.
Download: http://wiki.sharpdevelop.net/ilspy.ashx