You can add some real value to your site by adding links to dictionary sites. This is especially useful if you have pages with new terminology or difficult words.
A nice service is Dictionary.Com, which provides a full dictionary and a thesaurus.
If you have a computer or internet oriented site, then PcWebopedia may be perfect for you. This site has tens of thousands of computer terms with cross references and links to pertinent articles. It’s one of the best dictionaries of it’s kind on the web.