Splitweet is a new web based site, with Mac app (based on Fluid), to help manage multiple Twitter accounts. While they state it is for companies, I know too many people trying to start up multiple Twitter account for various reasons. Twhirl has been by local client of choice, even for multiple accounts. But sometimes you need a web interface that has different features.
To sign up I simply entered an email address to be verified and my primary Twitter account name (no password). I quickly verified and was in to a pretty clean interface. Based on the initial username I entered, Splitweet started pulling replies to the tweets that included that name into the bottom right side of the window.
I easily went to accounts and added the proper password for the main one as well as some others to see how the interface worked with multiple accounts on the screen. All the tweets are blended into one stream with color coding next to them. You are able to reply, direct, retweet and even favorite any of them you desire. The site auto updates the stream also on a schedule, which you can stop at any time.
At the top you are also able to send tweets to whatever account you decide. This is only a checkbox so make sure you are sending under the right one. I do like Twhirl for that since I know which window I am in most of the time.
Then there is a section for Brands. In this area you type in and save keywords that you want watched in the public stream. After I saved a couple, I went back to the homepage and it immediately started filling in the branding section with mentions of the keywords. This is a great way for users in companies to watch their company name or topic and respond. You could reply, retweet and direct message (if they follow you of course) any of the branded mesages pulled. I could then select which name to respond as also.
Overall a darn fine interface that companies should have users look at if they do not want to install local cleints. This also allows mutliple people to be in one screen and see everything at the same time.