I started a new download section for C# Subversion hooks. I've already put the Rss feed hook for check-ins. I will be putting up a skeleton project to get people started writting hooks in C# later in the week.
To see what's there please go to the Downloads menu, then Free Downloads, then Subversion C# Hooks.
Update July 31, 2008 - The file permission are now fixed. You can download it now. Please try and download the file again.