A lot of naysayers in here! You gents need to get more familiar with the command line.
So, after some fooling around, I found a command that will accomplish what you want...sort of. It will add the application to the right but when you click it, you won't get the blue dot underneath it nor will you be able to move it. The reason for this is simple (this is a theory based on the structure of the plist file that holds the values for the Dock) - the launchers on the right are part of a set that aren't interpreted as launchers in the same sense as the left side ones are. If we look at the icons on the right, this begins to make sense - stacks and the Trash behave very differently than the application launchers on the left.
Anyway, enough of the theory/explanation. To do this, you'll need to open up Terminal (/Applications/Utilities). Once open, execute the following to copy your current plist to the Desktop:
Code:
cp ~/Library/Preferences/com.apple.dock.plist ~/Desktop/
This will keep a copy of the working plist file on your Desktop just in case something goes wrong.
Next, copy the following but do not hit enter (yet):
Code:
defaults write com.apple.dock persistent-others -array-add '<dict><key>tile-data</key><dict><key>file-data</key><dict><key>_CFURLString</key><string>[COLOR="Red"]/Applications/Mail.app[/COLOR]</string><key>_CFURLStringType</key><integer>0</integer></dict></dict></dict>' ; killall Dock
The part that is in red needs to be changed. You need to replace that with the full path to the application that you want on the right side. Once you've made that change, hit enter and enjoy.
If something goes wrong, execute the following to copy back your original Dock plist and relauch the Dock:
Code:
mv ~/Desktop/com.apple.dock.plist ~/Library/Preferences/ ; killall Dock
To be fair, this is an adaptation of
this tip and it's not one of my own devising. I tried to do it on my own by analyzing the Dock plist but it didn't go so well.
EDIT: It might be possible to move them around if you have a plist editor installed (if you installed Xcode, you've got one).