As per the title, I'm interested to hear more examples of dark, gloomy or gothic sounding Ska or Reggae. The best examples I can give are:

The Specials "Ghost Town"
http://www.youtube.com/watch?v=jqZ8428GSrI

Madness "Grey Day"
http://www.youtube.com/watch?v=t-i5gzl3DZ4

Genies of the MA forums, fetch me more like these.

I recommend the first Rebelia album, Polish band. It gets really heavy at times too. I'm not sure if the whole album is on Youtube, I have it on cassette.

Generally very dark album, not that the lyrics don't have hope in them, they do but there is a dark gloomy atmosphere as of someone who has lost everything and is looking for hope. Although there are some upbeat songs on it.

Here's are some tracks: http://www.youtube.com/watch?v=XGjF8zQ1A2s
http://www.youtube.com/watch?v=XV2IlUhrsKE

Damn, that's some good shit right there, the heavy guitar work is a real bonus. Thanks a lot!