I am currently working as a Computer Officer at the Statistical Laboratory, University of Cambridge. For information about the computing facilities of the Laboratory, see my official home page.
The first roguelike I discovered was Nethack, in which you are an adventurer on a mission to recover the Amulet of Yendor for your deity.
I also play Slash'EM, a Nethack variant with lots of extra classes and races, new special levels and other new features. Slash'EM can also be downloaded from Ali's Slash'EM page; if you are in the UK you'll find this page much faster than the official Sourceforge site. I have written a collection of Slash'EM spoilers; links to them all can be found on my page of differences between Slash'EM and Nethack.
Another good roguelike is ADOM (Ancient Domains Of Mystery), in which your aim is to save the world of Ancardia from the invading forces of Chaos. ADOM has a much more complex plot than Nethack or Slash'EM, featuring many useful unique NPCs and multiple ways to win the game, but its user interface is not as friendly as Nethack's. For example, if you read a scroll and it isn't automatically identified, there is no way to name that type of scroll, unlike in Nethack. Here are more comparisons of Nethack and ADOM.
The best places to go for ADOM spoilers are Andy Williams' ADOM Guidebook and the ADOM Forums (web-based discussion forums where I post as Ekaterin). Here are a few spoilers I have written. These were originally written for version 1.0.0, but should be applicable to the current version.
I recently discovered Linley's Dungeon Crawl (or Crawl for short), in which your aim is to retrieve the Orb of Zot. The Crawl gods are much more distinct than the gods of Nethack and ADOM - there are several gods who like the character to dedicate kills to them, but the pacific Healer god actively dislikes this. The Crawl races are also well distinguished, both by physical features such as Centaurs being very fast but unable to wear boots and needing more food than average to survive, and by their aptitudes for different skills. For example, a Minotaur is very quick at learning to use weapons, while a Deep Elf is very slow at this but much quicker at learning magical skills.
You can download the original Crawl (which has not been updated for several years) or the Stone Soup variant which is still under active development. Crawl Stone Soup can also be played online at crawl.akrasiac.org, where you can find links to several spoiler pages. You can contribute your own spoilers and strategy guides to the new Crawl wiki.