Twitter recently introduced a feature on its website called "Who To Follow". This feature presents you with a list of people you aren't following already, but who are active in your social graph. However, I happen to be very proactive in finding new people to follow through a variety of means, and have no need for Twitter to point it out to me. I thought it was a bit obnoxious to see, especially considering both of my first recommendations were people I had blocked.
This Safari extension removes that box from the Twitter homepage, whether you have it turned on for you or not. It's a simple CSS stylesheet that sets display:none on that box. You'll never have to see it again.
You can download it here. I'm still a bit new at Safari extensions, but it should auto-update in the future if I ever release an update.
Update 9/18/2010: Follow Freely 1.1 has been released, with support for the new Twitter web client. It also fixes the issue where Safari would constantly say there was an update available.