Shaolin Dave
I suggest getting the free Unity3d engine.  If you don't want to create the point-and-click mechanics yourself you can buy the adventure creator for $70 (!/content/11896)

Honestly, creating the mechanics wouldn't be too difficult.  I might be doing it myself here shortly.

On another note, I love this C64 theme for your blog.  I think I might rip it off for mine... :)