Bukkit

This plugin was born about 5 minutes after my server crashed one too many times as a result of an exception generated from Multiverse. It stops players from teleporting to worlds or players that they don't have permission for. It uses the PlayerTeleportEvent, so it will intervene no matter what plugin the player uses to teleport (meaning it's compatible with all teleport plugins).

Requirements:

• Vault

Installation:

• Put it in your plugins folder
• Start your server

Permissions:

• dontteleport.<playername> (dontteleport.multitallented) prevents a player from teleporting to Multitallented. Apparently also works for groups (dontteleport.admin) if you use PermissionEx. Haven't tested it with other plugins.
• dontteleport.<worldname> (dontteleport.world) prevents a player from teleporting to anyplace inside the world "world"

Commands:

• None (use your permissions plugin to set limits on players teleporting with permission nodes)

Post Script: I managed to fix my Multiverse bug after ks answered my question in #bukkit channel on esper.net. His solution was to delete the .lock files in my world folders when my server was shut down. So far it's working. Multiverse is a great plugin with lots of features and a long history. It may not be the most up-to-date plugin out there, but it doesn't need to be. I recommend Multiverse, but if you want something more lightweight, then hopefully DontTeleport will be of use to you.