Print What You Like

PrintWhatYouLike lets you print the good parts of any web page while skipping ads and other junk.

NOTE: The service requires you to signup for additional features, but I've found that the non-registered version does exactly what I want. I personally don't need the other features. I would recommend you give it a go without signing up and make a decision after a few rounds with the standard version. 

http://www.printwhatyoulike.com/

Bookmarklet:  Add PrintWhatYouLike to your browser

Website Button:  Create a printer friendly version of your website

Sign up  for additional features:

• Change Sets: Save the changes you make to a page and automatically format other pages from the same site
• Clips: Save snippets of pages and compile them together in one document for printing