Development resources

Map File Format
Blocks, items and data values are common to all map types.

Map Formats

 * .dat Map Format
 * Map Format (NBT) 1 2
 * Alpha (InfDev) Level Format

Map Editing

 * Map Editing (general)
 * Map Editing (hex)

Libraries

 * Java Classes to Deserialize Maps
 * Java Class to read and write NBT structures

Schematic files are used by a few 3rd party utilities to store sections of a map for later use.

Server Protocol
Classic Server Protocol used by the Minecraft Classic Creative Multiplayer server.

For info on the protocol for Minecraft Alpha, see the TkTech wiki page as well as the authentication protocol here.