It's hard to pick a sample song for Doom Metal, as the albums usually need to be listened to in their entirety. Here's a sample from Slow's 'V - Oceans', which is still over 13 minutes long.
Doom:VS is another great artist whose albums need entire playthroughs. Picking a song is a little easier as 'The Faded Earth' is great.
I've followed Forest of Shadows since his days on MP3.com. Everything is the work of a single individual, and happy to say, he's still releasing albums.