That toolbar/ct plugin seems to cause problems for all who install it!
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!
Note: Safari does not support any third-party toolbars except those supplied as an extension to Safari via the Extension Gallery.