This is a Syntax Highlighter plugin for meant to be used with the new Blog4Umbraco package.
It installs the javascripts and css from Google Prettify (http://code.google.com/p/google-code-prettify/) and then inserts the a macro containing the references in the header, using an HttpModule.
This will highlight any code written in a <pre> tag like this:
<pre>
public void test()
{
string test = "test";
}
</pre>
This is a one-click-install on any site that has a <head runat="server"> element. If not, then you will need to insert them macro manually in your <head> element.
Let me know how it works for you :-)