I just noticed something in my testing.  I was searching for questions tagged "C#" and the questions come back tagged "C".

Code Poet's SOAPI javascript formats the route thusly:

http://api.stackoverflow.com/1.0/questions?tagged=c%23&sort=activity&order=desc

His works, whereas mine includes the "#" even when I HttpUtility.HtmlEncode it.  What am I missing, and is there a quick and dirty converter?