Huge amount of caves and abandoned mine shafts in 1.8:

Caves on a 2D map

(map source)

First preview version of Unmined is available for download.

Features:

• View 1.7 and 1.8 maps (overworld terrain layer only)
• Coordinate information panel
• Per-world cache and settings are stored in .unmined subfolder of your savegame

This is an archive site for the older releases of uNmINeD, a Minecraft mapper tool.

The new site is available at unmined.net.