Hopefully if you've been coding .NET for a while, someone has shown you Reflector, Lutz Roeder's .NET Object Browser and you have basked in its glory.
Surprisingly (to me at least) not everyone knows about Reflector's plugin model. There is a vibrant and active community of plugin writers out there, and you won't realize the full power of Reflector until you download some of these are start messing around. Seriously, if you thought that Reflector was useful today, just wait until you've tried some of these add-ins.
PowerShell Language Add-In
The one I've been messing with for the last few weeks is the PowerShell Language Add-in. Reflector can "decompile" (not the correct word) the IL within an assembly and show you the "intent" of that IL in any number of languages like C#, VB, Delphi, etc. Daniel "kzu" Cazzulino has created a PowerShell Language Add-in that, for the most part, shows you what the code would look like in PowerShell.
Now of course, it's important to note a few things. PowerShell is not (yet) a language that you can use to author .NET assemblies with. It is, however, an incredibly powerful scripting and automation environment. Sometimes the Powershell language (it is a language, by the way, with a formal grammar - here's a link (PDF)) can be a little confusing to learn, so the PowerShell Language Add-in is a really cool way to learn more about PowerShell within an environment you're already comfortable in.
Here's a reformatted snapshot of what's currently available.