When brands and companies use Twitter to reach consumers, more often than not multiple users are managing a single account by sending Tweets, monitoring streams for mentions of a brand, and responding to Tweets. There are a number of brand management-focused platforms that help advertisers and marketers manage social media, such as HootSuite, PeopleBrowsr, CoTweet, and ScoutLabs. BirdHerd, which is in private beta, is also part of this group and offers a lightweight tool for groups to manage a single Twitter account. We have 300 invites for TechCrunch readers; you can use the code “TechCrunch300″ when signing up for the service.

BirdHerd makes it easy for companies, brands, development and support teams, and other groups to update a single Twitter account. Using oAuth, administrators don’t have to give the contributors a Twitter log-in, they can use the service completely through DMs. Once an administrator adds the approved contributors to a Twitter account on BirdHerd, users can DM the main Twitter account with directions and updates, such as posting a new message, following a twitter user, replying to tweet, and more.

One of the virtues of BirdHerd is that it allows contributors to update a Twitter account from another client, such as TweetDeck, Seesmic or even Twitter. Another compelling feature is the ability to allow users to share all DM actions and who sent them on a given account with other users. And the service prides itself on its simplicity as a platform; BirdHerd isn’t nearly as comprehensive or feature-rich as some of the other brand-focused clients.

Of course, BirdHerd’s main competitor may be Twitter itself. Twitter has been rolling out its own contributors feature, which allows multiple people to tweet from one account (with individual attribution below the tweet).