GoBetween is a lightweight Bukkit plugin that logs a player's location when he changes worlds, thereby enabling him to later return directly to that same location.
This plugin offers support for "world groups" - multiple worlds that are treated as one for teleportation purposes. This allows administrators to, for example, "bind together" a survival world and its nether counterpart, storing only one location per user for both worlds. To make use of this powerful feature, edit the appropriate sections of config.yml.