Ping-O-Matic - Service to update different search engines that your blog has updated.
TotalPing! - Promote your blog with TotalPing!
Pingler - Pingler is a tool that allows you to ping your blog or website, so that followers can know if your site is online after any update, maintenance, etc.
PingMyLinks - PingMyLinks is one of the oldest websites in the internet marketing industry that you can use to index your websites and blogs.
PingFarm - PingFarm is a service that uses an API to notify search engines when your blog or website has been updated.
PingMyBlog - PingMyBlog is an online service that notifies you about all the major bogs directories in one go.