Where is addressbook:// stored I wrote an applescript that finds a person in my contact list.

tell application "Contacts"
    set thePeople to first person whose first name is equal to "John" and last name is equal to "Doe"
end tell

tell application "Finder"
    set theURL to "addressbook://" &amp; id of item 1 of thePeople
    open location (theURL)
end tell


The addressbook:// will open the person in the Contacts app.  But I installed the Cobook app and it opens now instead of the Contacts app.

Where is the information stored that says open Cobook with addressbook:// and is possible to have two entries so that both Cobook and Contacts open?
The file is the LauchServices plist file. It is at 
~/Library/Preferences/com.apple.LaunchServices.plist

You can edit it manually, or is you plan to do this a lot, I'd suggest looking at RCDefaultApp which gives a preference pane for editing.