Personally, I like the Google Ads, but if you don't, you may want to try this URL from Google to search.
A search for "ipod" brings up about nine ads on the main Google Search. But the same search on www.google.com/search?output=googleabout displays no ads, but the same exact organic results.
I spotted this at DigitalPoint Forums but I believe this originated from TecheBlog, but I am not 100% sure.
How did they figure this out? It was not brain surgery. Go to any of the About Google pages, for example here and on the left side is a search box that says "Find on this site." Enter your search query there, let's say for ipod and up come results for ipod matches found at google.com.
Right, I know, that is not what you want. But by simply removing the "&sitesearch=www.google.com" parameter from the URL, you are opening up the search to all sites. Yes, ad free.
Forum discussion at DigitalPoint Forums.