So I have been doing allot of custom cocoa URL code over the last week, so I thought I would go look around for applications that have custom URL types. In my search I found the following url type for TextMate (txtmt). Here is an example that will open up text mates own info.plist and show you were these are declared.

txmt://open?url=file:///Applications/TextMate.app/Contents/Resources/Info.plist&line=&column=36
Here is an example of this link
There is a quick blog post about it here on their site. All in all I can see some pretty cool ideas for this, such as what I am big fan of which is interactive documentation. I am a big URL nerd and to mention one other cool one I knew about previously is transmit’s transmitreg:// which they use for serial numbers ,an awesome way to fill in serials that every vendor should do.