The Ping-O-Matic plugin pings http://pingomatic.com/, from where your ping gets relayed to a set of most common ping services.
This hack allows you to show and hide categories using toggled divs - not a copy of the expandable categories hack! I got it working from some help from another b2evo person, but thought it would be useful for others as a hack. I have the hack working on my site in the sidebar - works for version 1.10.
The Generic ping plugin can be used to add a generic RPC ping service to your blog.