I have registered more than 30 press release sites, they all bring trafic to my site <snip> Till now, I haven't found google penalized my site. Just write some useful and high quality articles. They are great places to build backlinks to your site and promote your business.
[edited by: bill at 6:40 am (utc) on Oct. 8, 2009] [edit reason] No personal URLs please [/edit]
I sent a release using ereleases.com about a year ago and got great media coverage. Which in turn, built credibility for my site and produced some solid links. I've recently used prweb.com and didn't have much success. Frankly, I think that has as much to do with the content of the release rather than the platform.