SocialOomph is one of my favorite Twitter tools. The free version is loaded with powerful features. You can:
- Schedule Tweets
- Track Keywords
- Extend your Twitter profile
- Save and reuse drafts
- Automatically send a welcome message to a new follower
- Shorten and track your links
- Follow those who follow you
- Vet New followers view @mentions and retweets across multiple accounts!
- Purge your DM inbox