Here is a large list of sites you can submit your press release to free of charge: http://www.webmaster-elements.com/submit-press-releases.htm
I guess these links were already shared many times. It would be cool if someone shares some other links which aren't covered earlier
I don't necessarily find links like this very useful. Often, you will have better results using the top 3 sites in a given category, than using ALL of the remaining 97 sites. Focus on quality, not quantity, and don't waste your time using a site unless you have reason to believe that it'll actually produce measurable benefits.