I know it's a bit late, since Notch has stated new content is finally going to be coming to the game more regularly, but what are peoples favorite mods, if you use any?
So far all I've done is had a play around on the Skyland map/project. A real good bit of fun, but not really a mod per se. Once Notch has added a heap more content and mod support, no doubt there will a birrion different excellent (and terribad) user made maps/adventures/scenarios etc.
But for now, what modification files have you used, and have any been good enough that you've kept on using it as part of your Minecraft experience?
Currently requires hMod, will work with Bukkit when that comes out.