See also: Debugging tools
About obfuscating in general
The main purpose of obfuscator is to protect intellectual property of the software.
Eazfuscator.NET is a free obfuscator for .NET platform.
ILMerge is a utility for merging multiple .NET assemblies into a single .NET assembly
YES! I didn't download any new release, but I'm still marking yours as the correct answer (the only one at the moment...) because it led me to visit Mike Barnett's page where he described using /targetplatform:v4,<path to your v4 framework directory> instead of /targetplatform:v4 /lib:<path to your v4 framework directory> http://stackoverflow.com/questions/2961357/using-ilmerge-with-net-4-libraries
- de4dot - Deobfuscator for .NET
- de4dot - Deobfuscator for .NET - Sourcecode (help at buttom of the page)
- de4dot - Deobfuscator for .NET - Download