I wonder if there is a way to precompile *.less files(http://www.dotlesscss.org/) with visual studio.
The site gives me a dotless.compiler.exe
You may want to take a look at Chirpy. It has a lot more support than just LESS. I wish I would have found it prior to writing my own.
Speaking of which I also wrote a Visual Studio Custom Build Tool that executes using the JS file (instead of the .NET port) you can take a look at the source here: https://github.com/paultyng/JsBuildTools
Or it is also on the extensions gallery under JsBuildTools.