SEO stop words are basically words that Google skips over while spidering your site.
Here are some good articles, resources and lists for SEO Stop words.
http://www.link-assistant.com/seo-stop-words.html
http://www.stomperblog.com/seo/seo-stop-words-and-say-hi-while-youre-here/
http://tools.seobook.com/general/keyword-density/stop_words.txt
