Angband is a free, single-player dungeon exploration game where you take the role of an adventurer, exploring a deep dungeon, fighting monsters, and acquiring the best weaponry you can, in preparation for a final battle with Morgoth, the Lord of Darkness.
The most recent release of the game is version 3.1.0 beta (released on 7th January 2009), and you can download versions for supported platforms from this page, or the source code if you want to compile it yourself.
Getting started with the game is easy. You can play with graphics or in original ASCII text (it's more fun than it sounds), and there is extensive in-game help. Pressing 'Enter' also brings up a list of commands you can choose from whilst you're getting started.
Angband has an active community, split mostly between the forums and the newsgroup. If you enjoy the game, you might want to take a look, as hints and tips are often shared, and those asking for advice are welcome.
For more information, see also: Gameinfo:Angband