I am a big fan of Bookmarklets. They don’t take up RAM and get straight to work when, and only when, you need them.
I’m also a big fan of Copyscape. It’s a really quick and easy way to test page content to see if it has been duplicated on other sites. You just enter the target URL and it returns a list of pages with similar or duplicated content. Clicking through the results you can see each page with the duplicate content highlighted.