Love the dictionary plug-ins for Firefox.

I like to use GuruNet. Alt-click on a word and you get dictionary, thesaurus, translations, and (if you pay) more. Works with any program that displays text.

Well, I've been using it for years with no hint of intrusive spyware. Ad-Aware, Spybot, and Spy Sweeper all pass right over it without question. Norton firewall asks about it whenever I fire it up for the first time on a machine, otherwise not a peep.There is a privacy policy, a little difficult to locate, at http://www.gurunet.com/privacy.jsp. Also see Does GuruNet contain Spyware? | www.infopackets.com.