I've upgraded the GreaseMonkey Google Navigator script to fix some minor issues with the next and previous keys in groups.google.com and I've added the "open link in new tab" functionality via the 't' key. Check it out:
http://userscripts.com/scripts/show/3984
Or right here at:
http://www.pragmaticprose.com/content/binary/googlenavigator.user.js