Even the best writer's get stumped for the rigth words.  If you've hit writer's block while attempting to do some advertising copywriting, knocking out a sales letter, or pitching a proposal to a new a prospective client, try these two helpful online sources.  

The Visual Thesaurus is an interactive dictionary and thesaurus which creates word maps (somewhat like mind maps) that give the meanings of the words, and then branch to related words. It's a great way to brainstorm for the perfect word in a more multidimendsional way than using a regular printed thesaurus.    It's an affordable software tool, and is available in a desktop or an online version.

Lexical FreeNet - Connected Thesaurus.  This is a free service.  Just type in a word, and you'll find related words, concepts, and even rhyming schemes.