If you have various twitter accounts i.e. a personal account and a brand account that you manage, you could definitely use Tweetdeck. It is a browser that enables to you to view your various accounts simultaneously. You could also post your tweets, or schedule them using this tool.
Per their latest update, you can also use tweetdeck not only for your twitter account but also for facebook, google buzz and even foursquare accounts. Check it out at this link http://tweetdeck.com
