The focus is on tweets containing links, with the goal of giving you a window into content being shared on your watched topics by people you don't necessarily follow. Next to each tweet is a short preview from the link it contains, giving you a bit of insight about whether or not it's worth following the link.
A service from the folks at social news site Mixx, TweetMixx lets you log in with your Twitter account via OAuth and add a set of your interests to follow on Twitter. It's more intelligent than simply a saved search though -- it's unclear what algorithm they use to identify what falls into "tech" or "gaming" for example, but so far the results seem quite accurate for the topics we've followed.
You can also get a view of the links being shared by just the people you follow (and a toggle to view all tweets regardless of whether or not they contain links), with the same link preview service displayed in the middle column. Like Facebook and Twitter Search behave, as new updates come in the site will notify you with a message at the top saying "There are more tweets to be read!" and a link to refresh the page.
In the far right column is a textbox for updating your own Twitter status which is standard throughout the "your interests" and "your friends" sections, creating a nice all-in-one dashboard for finding relevant content and sending it back out to your network if you wish.
Top Content and Trends on Twitter
Two other tabs in the horizontal navbar include "top" and "trends," giving you a window into what content is hot and trending right now on Twitter. This is similar of course to what TweetMeme and some other services do, but having this combined with topic following and link previews makes TweetMixx a valuable new contribution to the crowded web-based Twitter interface service field.