Hi seo.expert,
LoL You are seo.expert then you should know about them? LoL
Anyways, Pressrelease are very important from SEO view point.
They are information you submit to some sites, along with your site's link. If this information gets published your site can get instant boom in SERPS.
They also provide a BL to your site.
The information you submit should be descriptive and should not look like you are benifitting your site.
I use following two sites for press release.
www(dot)digg.com
www(dot)pressbox.com