What are some good online press release sites that can distribute my article?

I'm looking for a company that can distribute my press release being used mainly for SEO purposes.

Here i mentioned some of the most popular press release sites :

aip.org/pt/pr.html
nps.seeamerica.org/pmgr?press=prForm
software.newsforge.com/submit.pl
www.npr.org/about/pitch/story.html
prndirect.prnewswire.com/
aiim.org/add-press-releases.asp
www.betanews.com/submit
www.edn.com/index.asp?layout=pressReleaseSubmit
www.nanotech-now.com/submit-press.cgi
www.programmersheaven.com/other/submitnews.asp