www.weblogs.com

          Weblogs.com is a ping server run by Moreover Technologies that automatically notifies subscribers when new content is posted to a website or blog. Essentially it acts as a central hub between publishers and consumers of content: Publishers notify the community at large when new content is posted, so that large-scale consumers of content (such as search engines) don't have to guess or blindly poll sites to check for new material. By creating a more efficient interchange between the two sides, content can be indexed and distributed more quickly, as close to real-time as possible.

         Weblogs.com is the original ping service on the web and receives millions of pings every day from blogs, news and other information sources that have configured their publishing software to notify   Weblogs.com the moment new content is published. Many of the large blog publishing platforms automatically ping Weblogs.com on behalf of its users.

          Weblogs.com is a free, open service and everybody with a blog or website with updating content can ping it. 

Link: http://www.weblogs.com/

www.pingomatic.com

           Ping-O-Matic is a service to update different search engines that your blog has updated.

           It regularly check downstream services to make sure that they're legit and still work. So while it may appear like it have fewer services, they're the most important ones.

          Make sure to only ping specialized services if they're relevant to your blog, otherwise you'll cause an undue burden on them.

Link: http://www.pingomatic.com/

www.auto-ping.com

Auto Ping

           Auto Ping notify search engines, blog and rss directories that your blog is updated or created. The benefits are faster Search engine indexing, increased visibility and more traffic. And it only takes less than 30 seconds to do this with its blog ping tool which is completely free and easy. Works for any type of blog or site. To ping your current page, you click in image link (example shown below) from your website or blog.

Link: http://www.auto-ping.com/