CodeDefender
Open source .net "empty string based" obfuscator to protecting your (C#, VB.Net...) CodesThis application designed to help .Net developers easily protect their codes. CodeDefender obfuscates and protects your code.
Not In Feature!Create meaningful source from CodeDefender protected binary.

At least you need .net framework 2.0 to run this tool and Visual Studio 10 to open source project.