Agalloch should really get much more credit than they do, personally I find them better than Opeth. They have a similar sound and themes throughout their songs. Don Anderson, the lead guitarist of this band has a side project which is probably my favorite metal band, Sculptured; Avant-garde/Progressive metal.
Cynic though they are pretty popular, people don't give them credit because they get lumped into the Death Metal scene.
Daylight Dies, very good melancholic Death/Doom metal band
Earshot easy to listen to alt metal/rock band, singer sounds a lot like MJK of Tool
Feos is a one man shoegaze/black metal project that is very good
Giant Squid is a really catchy Sludge group who recently released an amazing album
Ihsahn is the project of one of the guitarists of Emperor, it has obvious black metal influences, but it also has a power metal overtone.
November's Doom is a band that doesn't have a big fanbase, personally, they sound like just another Death/Doom metal band, but they have a good sound, they just don't do much with it sadly.
Katatonia is a good Doom/Dark metal band out of Switzerland, the Jonas Renske of this band and Mike Akerfeldt of Opeth are good friends, they formed a small, short lived outfit October Tide. Mike and a few of the band members of Katatonia and other musicians formed the group Bloodbath which is a good Death/Gore metal band.
Warning is a good traditional Doom band. on the same coin, Winter is a good Funeral Doom/Death metal group which share a lot of the same influence.