Seriously noone has mentioned Unique Article Wizard? Check it out it blows the other 30 or so article writers I've tried out of the water. It contains a synonym database updated by users so the synonyms actually make sense and are available for entire phrases as well. There is no magic pill that lets you click a button and bam you have a new unique article. That doesn't and will never exist so stop lookin if you are(or squander your hard earned $ on failware)!
Spinnerchief does indeed a good job (although it has other flaws like crashing at startup occasionally)...and spinchimp (although i LIKE the interface!) gives a very weird list in his thesaurus, like the order of the synonyms is not as good as with spinnerchief. TBS i haven't used in ages, as said we do only MANUAL spins so we don't in fact need most features many spinner tools have today.
The website ranking game has completely changed in the search engine arena and a websites authority and relevant content is much more important. Producing factual and good quality articles can earn votes from people sharing the content across the many social, website and blog networks around the ever expanding internet landscape. These votes alone produce favour with the search engines and can shoot a website up the rankings rather quickly.
To rank your website in search engines you have to post content at your website on daily basis. If you have more than 2 websites then it is almost impossible to write unique content on all those websites. To do this task webmasters use article spinning tools so that they can post articles to their domains daily. Paraphrasing Tool is also used by students when they have less time to submit their assignment; they just copy content from the internet, rewrite it, remove grammar mistakes and submit it.