WorldPainter is an interactive map generator for Minecraft. It allows you to "paint" landscapes using similar tools as a regular paint program. Sculpt and mould the terrain, paint materials, trees, snow and ice, etc. onto it, and much more.
WorldPainter is implemented in Java, which you should already have if you're playing Minecraft. If not, install Java first from here.
Download the program here:
(all versions of Linux; can be installed as root or as a regular user)
RPM package: download (Red Hat, Fedora, etc.)
DEB package: download (Debian, Ubuntu, etc.)
Note that the Linux/UNIX versions of WorldPainter need Java 7 or higher.
If you have trouble installing the program using one of the installers above, you can download installerless archives here: 32-bit Windows, 64-bit Windows, Mac OS X and UNIX/Linux. Note that these are not recommended and unsupported!
There is not much documentation yet, but the program should be pretty self-explanatory. To play the map, choose Export in the File menu. Just experiment and try everything out. Don't forget to check the menus, and to see what happens if you right-click instead of left-clicking.
For support, go to the official thread on the Minecraft forums.
You can also donate bitcoins! Scan this QR code with a Bitcoin app, or click it if you have a Bitcoin client installed on your computer. If all else fails, the bitcoin address for donations is: 1NK8PFYFetTiWReujPsQXDcarXKJuYtqgF.
WorldPainter was created by pepsoft.org, a one man Java software development company from the Netherlands. It is not affiliated in any way with Mojang and has no official status. WorldPainter includes the work of many others - the credits page lists them.