Open Source Alternatives to Reflector?

Another replacement would be dotPeek. JetBrains announced it as a free tool. It will probably have more features when used with their Resharper but even when used alone it works very well.

User experience is more like MSVS than a standalone disassembler. I like code reading more than in Reflector. Ctrl+T navigation suits me better too. Just synchronizing the tree with the code pane could be better.

All in all, it is still in development but very well usable already.

Updated 13th December 2011

The following open source tools are available:

• ILSpy from the SharpDevelop team. Thanks to Scott Hanselman's tweet highlighting the tool.
• Dotnet IL Editor (a disassembler)
• IL.View - a .NET Reflector alternative written in Silverlight 4 as an Out-of-Browser Silverlight Application. See this blog post for details.