Essentials for making Maps! :)

If you want to make some maps, then heres the mods you will want to have!

Too Many Items!
Too Many Items is an ingame inventory editor.

Good for fast item spawning!
http://www.minecraftforum.net/topic/140684-173-toomanyitems-in-game-invedit-july-1/

Single Player Commands!
This mod allows you to have most of the Bukkit Server commands in single player! And it also includes World Edit!

Really epic mod!
http://www.minecraftforum.net/topic/94310-173-single-player-commands-v210-2/

Zombes Mod Pack
If you want to make a map with friends on a server, then use this to get fly-mod in multiplayer!
http://www.minecraftforum.net/topic/91055-v173-zombes-modpack-26-mods-v430-upd-24jul/

Zombes mod pack is really useful, you can select the mods you want easily. I would recommend backing up your Minecraft.jar file/Bin before you attempt to install it.

TooManyItems is really useful because you simply click on the item you want and it will be sent strait to your inventory in a stack of 64 (Except signs, etc).

Singleplayer Commands is one of the best mods for Minecraft, there are loads of commands, just go to the Minecraft Forums topic and all the commands will be there.

NOTE: If you are making a map, make sure you use the texturepack!

We dont have a texture pack yet but we are asking you, the community to help make a 32x32 texturepack for everyone to use

Bioshockacid whatever his name is, could do a good job.