McChunk
Minecraft chunk deleter
Copyright 2011 Michael Barriault

Features:
-Renders top-down 2D render of a world
-Click-and-drag chunks
-Press Command+Delete to delete chunks - immediately saves

Upcoming features:
-Scaled rendering for large worlds
-Easy multiple chunk selection
-Rearrange chunks

Known issues:
-Map is rotated and mirrored.
 -North is left
 -South is right
 -West is up
 -East is down
-Memory intensive. Seems to cost about 100 MB of RAM per region.
-Memory leaks very likely.
-Debug info is abundent, will clog up your Console.
-Only works on zlib-compressed worlds - shouldn't be an issue for vanilla (both
 SSP and SMP) worlds, and even most Bukkit worlds (unless you're using a plugin
 that uses a different compression scheme).

Howto:
-Open app
-File->Open
-Choose folder containing .mcr files.

Recommendations:
-Strongly recommend to back up first. This app comes with NO GUARANTEE. The
 region files are saved AS SOON AS YOU DELETE. There is no built-in backup.
-This renders a 1 pixel = 1 block top-down image of the entire world. Only 
 having a few region files at a time.

For example!
You have a region folder that contains a lot regions. They're named like
    r.0.0.mcr
    r.0.1.mcr
    r.0.-1.mcr
    r.1.0.mcr
    r.-1.-1.mcr
    ... and so on...
These numbers represent a X,Z coordinate system that are related to the in-game
coordinates by multiplying by 512. If McChunk is crashing on your world, try
moving some .mcr files out of the region folder temporarily so that the ones 
that remain are all connected but represent a much smaller region.

The SMP server I run, with 37 region files, crashes McChunk on my MacBook, but
runs just fine on my iMac (quad-core i5, 12 GB of RAM).