Forgive the shameless plug here but HireScores.com is on Twitter and you can folklow us here:
www.twitter.com/HireScores . That aside I personally am becoming very addicted to Twitter. The conversational possibilities are endless and I could understand if people are using it during work time that it could take up a good chunk of your day. Ultimately it's like sending a text message. If your boss has no problems with you texting from work then it's probably ok. If they do mind? It probably isn't ok to tweet during work hours.