Now this is interesting. Our old friend Jesta, who made the EpicAdvice.com site not so long ago, is working on a new project at EpicPlan.com, and while it's still hidden away in pre-alpha, you can see what they're up to in this thread on EA. It's a slideshow/diagramming web app, basically -- you can take maps of the game's instances, lay out icons and symbols on them as you wish, and then animate and caption boss fights and encounters. The end result is a very clear way to show off different raid strategies, and we're told the slideshows are embeddable on other sites as well (you may even see some here eventually on WoW.com).
Unfortunately, they're only taking signups for the beta of the service right now, and while you can watch a show in action on the technology demo, you can't make your own quite yet. But it seems like a very impressive tool for raidleaders, both to share plans with the public and players seeking help, as well as your own raid members. It'll be great to be able to make a quick and easy visual display of where to stand and what to do during boss fights and instance encounters.