HightlightLine is a project mainly written in C#, it's free.
Visual Studio 2010 extension to highlight the current line
HighLightLine is an extension for Visual Studio 2010 that sets the background color of the current line to a user settable value. It's based on the http://visualstudiogallery.msdn.microsoft.com/0cc4c4c5-0f0b-4c6b-a269-3e0c1603d516[LineAdornments] addon except that HighlightLine:
To change the highlight color open the Options item in the Tools menu, go to the Environment tab, select "Current Line" from the Display Items list, and set the background color.
To install exit studio and double-click the vsix file. To uninstall use the Extension Manager item in the Tools menu,
To check for newer versions of the extension visit https://github.com/jesse99/HightlightLine[github].