Scans post for links, checks if they are pingeable and sends pingbacks with results returned, improves chances of successful pings!
Pingchecker is a free plugin for WordPress that allows you to scan your post's content for links, check the pingability of those resources you've linked to, and manually ping those pages. This improves upon the inbuilt fuctionality of WordPress by allowing you to receive the results of your attempted pings whereas WordPress doesn't. (With WordPress your ping either appears in the trackback list or it doesn't, with no explanation or error codes.)
Also included is a workaround for a bug in the WordPress XML RPC server that prevents many of your pingbacks from succeeding without you even knowing about it! When you ping another blogs server, it will check the page you linked, BUT because of this bug, sometimes it can't find the link at all. This workaround adds a hidden div to your footer with your links so they can be found, greatly improving your chances of a successful ping.