I ran across Twalala accidentally (read this about page for a great rundown) and from first glance I am glad I found it. It is strictly a web based client, but it has some cool features. Right from their site:
Using twalala, you can filter tweets out of your stream by keywords and phrases or mute individuals who get a bit too chatty. Finally, Twitter with a mute button
This has been needed for some time, if it can only start grouping and have a desktop client, this would be even better than it is so far in theses early stages.

Courtesy of Twalala
Your own tweets show up in yellow highlight and you can mute a particular person for w hile, a phrase or tag or even set an exception to the phrase muting for specific people. Wow.
UPDATE: I would like to suggest a logout button at the top also, not just after I scroll all the way down the page
Filed under: Web Clients , Twalala