I have been addicted to twitter and thus tweetdeck for a long time now , But the heavy dosage of ram taken by tweetdeck (along with the notifications) was always a off to me.
Two essential things you will find running on my desktop are Google Apps (On firefox ) and Tweetdeck (as a program), And thus idea of integrating both functionalities into one was just irrestitable .
TwitterGadget is a awesome piece of opensocial gadget that integrates into your gmail interface. Replies and DM’s are highlighted with a different colour (Overall it has same look and feel of Twirhl).
Since it’s on opensocial you can easily integrate it with igoogle, gmail and google apps. Choose whatever you want.
Here’s a quick 5 steps intro for installing twittergadget on google apps account. http://www.twittergadget.com/how_to_install.html