Here you can find ValaBinding plugin for MonoDevelop. The same plugin works on Windows & Linux.
I do not develop it longer. I started creating Vala plugin for IntelliJ, which is much better IDE. Unfortunately, this is not an open source project at this moment.
Version 5.0 works with MonoDevelop 5.0 and 5.1 and was tested on Windows with Xamarin Studio 5.1.4.
Version 5.4 works with MonoDevelop 5.4 and was tested on Linux.
To install, copy ValaBinding.dll to monodevelop/AddIns/ValaBinding folder (/usr/lib/monodevelop/AddIns/ValaBinding on Linux).
For Windows, you may want to try my portable package (includes MonoDevelop 5.1.4, valac 0.25.1 and mingw64 4.9.1).
The project is located on the git-hub: https://github.com/marek-g/ValaBinding