Here is a convenient javascript bookmarklet for CBAS. I have only tested it in Firefox so let me know if it works ok in other browsers. Of course you will need to have a javascript enabled browser.

Right click on the below link and save it as a bookmark.

To use the bookmarklet when you are browsing the web, simply right click an image you'd like to search for and select 'view image'. This will put it's URL in the address bar. Now click on the bookmarklet you saved and it will perform a CBAS search with the URL currently in the address bar as the search criteria.