Look It Up
By Gavin Shapiro, this program gives dictionary definitions and theasaurus synonyms with ease.

CleverKeys
With this free utility you can look up words in almost any program! You can also find synonyms from Thesaurus.com and search the Web. For Windows or Macintosh.

NetSmartz
The NetSmartz Workshop is an interactive, educational safety resource that teaches kids and teens how to stay safer on the Internet.