Maybe a lot. Check out searchCrystal to find out. SearchCrystal is
“a search visualization tool that enables you to compare, remix and share results from the best web, image, video, blog, tagging, news engines, Flickr images or RSS feeds.”
So what does that mean? Basically, you go to the site, enter your search terms, pick your type of search (web, images, video, news, blogs) and hit search. SearchCrystal then searches five search engines – Google, Yahoo!, Ask, Exalead, and MSN – and gives you a visual, color-coded representation of your results. You see hits unique to each search engine and you see which hits that more than one search engine found. If you don’t like the “cluster” view, you switch to a bull’s eye or list view.
It takes a bit to catch on to all the symbols, but once you do, you will quickly be amazed to see how much you’ve been missing if you’ve been using just one search engine.