What is pinging
Pinging is telling search engines directly that you have a new content on your site. And most of these pinging websites will update others like Google blog search, feedburner My yahoo, Weblogalot and many more.
Where to ping
These sites are famous for their pinging services
How to Ping
When visiting these ping service sites, all you have to do is put the URL of your blog, sometimes they require you to put post title and some allows to submit multiple URL'. Remember to ping only when you have a new content, if you ping and nothing new was in there, it will be seen as a spam.
Pinging alone can't increase search engine ranks, however it will help for your content to get found by big search engines faster.