ILSpy, JustDecompile (substitutes for Reflector)

ILSpy: 
.NET Decompiler

ILSpy is the open-source .NET assembly browser and decompiler.

Development started after Red Gate announced that the free version of .NET Reflector would cease to exist by end of February 2011.

ILSpy requires the .NET Framework 4.0.

---

JustDecompile
(by Telerik)

Unrivaled decompiling power.
Proven 10 times faster.
Free, for everyone, forever.