I have seen people mention dynmap on vanilla servers but no actual guide or instructions on installing it for vanilla servers. With bukkit you just stick the jar in the plugins folder. I want to figure this one out because I like dynmap.
This is something I've heard of. I don't think it's real-time dynamic but it gives you a map of the world which I assume you can schedule to re-render daily or whatever you want. I assume it doesn't give you the indicators of where players are though.