Instant Username Search - Check out if your username is available
SocialPilot - SocialPilot is an app designed to help businesses and professionals with social media marketing.
Namechk - See if your username is available on 100+ social networks
Fomo - Fomo turns your site into the online equivalent of a busy store
Handlescout - Get notified when a Twitter username becomes available
Buzzstream - Build Relationships. Build Buzz. Web-based software that helps the world’s best marketers promote their products, services and content.