During the recent google farm update, ezinearticle and articlebase were one of the top sites, who lost their rankings, because they staged spinned contents. Both these sites are still not penalizing those users who submit spinned content. But, they make some actions in the future. Spinned articles may just lower your reputation.
If you still want to go for one they you can search for article spinner by submit suite.
If you intend to use Article Spinning as a part of your link building strategy, I guess you're making a wrong move. After the last update of Google's Algorithm, creating a good, unique and informative is always considered...
Article spinning works if you spin it enough. If you simply replace a word here and there, your article would be considered very week. It will take you at least half a day (usually much more) to produce a good article to spin.
Most of the software out there is paid for. I've not come across one that's for free.
I think article spinning can be one of your option as long as you edit/polish the article after spinning. What I do is , I mix around 3-4 articles on the same topic, spin them and re-write... And VOILA! I always get positive results.