I love http://hilite.me/. It allows for some really nice options for blog syntax highlighting for multiple languages, C# being the one I'm most concerned about. It also has different styles to meet someone's needs. I just stick to VS which mimics Visual Studio pretty well. Another nice feature with this highlighter, is the fact that the code is separate from the line numbers! This make for easy copy and paste... Not that I condone copy and paste coding...
Here are a couple examples:
And default styling with no line numbers: