Is there a way to find where other players are in the Minecraft world without asking them for their coordinates? I play with friends. We've sort of aligned ourselves in a 2 vs 2 match-up, and since we wanna PvP with them, we need to find them first.
No, not without mods (and even then this is functionality most modders don't care about creating). You're going to have to hunt them the old-fashioned way.
Look for signs of passage: half-harvested trees, temporary shelters, mined ore, cobblestone. Lay traps: place tempting things and wait in a camouflaged spot. Find their base(s).
Yes, you can share a map item on a multiplayer server.
If you have a map, you can "clone" it to create an exact duplicate. It will show the same explored area on each clone, and all players who are using the map can see player arrows for each other. I have tested this with my brother on our server.
To clone a map, put the Map item to be cloned and one or more Empty Maps in the crafting grid. You will get 1 clone per Empty Map.
For more information, see: http://www.minecraftwiki.net/wiki/Map_(item)#Cloning
My Bukkit plugin Mapcoords has a command
/mc find [player] that will tell you the coordinates of a player.
Best solution, Dynmap. Could keep it secret if you were to choose so (easily done simply by keeping the port secret or changing it if discovered). Cursor position displays location readout on the upper left of the screen. Shows all server worlds.
This is my server dynmap (copy & paste):
Have a look at it to get the feeling of how the plugin operates.
Here is the link to the Dynmap Bukkit page:
And finally here's a great vid explaining how to setup and use:
Once installed and ready, you can basically customize it to almost as far extent as you could a website. Hope this could help!
This answer should be credited to @QbsidianH20 , but if you are op, or at the server console, you can use:
/tp <Player/Entity> ~ ~ ~ –
This is a teleport command. The tilde means relative, but with no additional values, it wont actually move them. It will however display their coordinates in the console.