Youtube

Several people have posted videos on Youtube about Nethack. As 2010 began there were well over 700 [] (Link to Search). There are musical videos, parodies and other fan material as well as lots of gameplay excerpts.

A few people have diligently chronicled their repeated attempts to ascend with the Amulet. The two main series are...

The Nethack Diaries
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(Link to Playlist) The Nethack diaries follows an unspoiled Finnish player trying to beat his best level in the Dungeons of Doom and covers 24 videos.

Lets play Nethack!
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(Link to Playlist) This is a more protracted series through the Dungeons from a more knowledgeable player, who tends to get unstuck in the Gnomish Mines. It covers 152 videos.

Time Lapse Ascensions
There are also several 8-10 minute videos which show a sped-up ascension all the way through which are perhaps more instructional.