That toolbar/ct plugin seems to cause problems for all who install it!
If you are running Tiger or Leopard:
Close Safari, then locate and delete the following files and it should be gone:
/Users/<User name>/Library/Application Support/Conduit
where / is the root library on your Hard Disk.
If you are running Snow Leopard you should also look here:
Library/Application support/conduit plugins
Also, as mentioned by Gilli2000:
Library/Receipts - If you read it, it has information in it at the bottom referring extensively to "CT" and "community toolbar".
Maybe it is harmless, but trash those items anyway!
If you are running Lion:
From the Finder Menu bar, select Go ▹ Go to Folder, and in the box that opens write:
Delete the second item if it is there.
Now select Go to Folder again and enter /Library
From the folder that opens, delete the following items if they are there (you may need your login password):
then close the folder. Now select Go to Folder again and write: /Applications/Toolbars
Delete that item and close the Finder windows you opened. Log out then log back in, and you should be rid of it.
Note: Safari does not support any third-party toolbars except those supplied as an extension to Safari via the Extension Gallery.