Doesn't exist yet. Check this website, the 1.5 Bukkit will be posted there when it's done: http://dl.bukkit.org/downloads/craftbukkit/
then whats this? http://www.planetminecraft.com/project/bukkit-15/ people say it works idk. EDIT by Moderator: merged posts, please use the edit button instead of double posting.
thats some bukkit 1.4.7 someone edited and forced protocol to let 1.5 clients to join. please remove link.
It's not Bukkit posting it, others have gotten impatient and made partially working (but also partially broken) hacks of 1.4.7 that allow 1.5 clients to join.