Everyone keeps saying it, and it's true: there is nothing quite like DTB.
The people who have mentioned Silverchair's "Diorama" album are on the right track, though. Forget all their earlier albums, it's on Diorama where Daniel Johns finally comes into his own and is able to express an incredible range of emotions and styles. There are similarities to DTB (and indeed other Dev albums such as Ocean Machine & Terria), mainly in the epic arrangements and lavish orchestration. Where Dev assaults our ears with multiple guitars, keyboards and ever-thickening of background vocals in a (mostly) metal-flavoured stew of beautiful brutality, Daniel Johns shows his vision of rock music through more of an orchestral film soundtrack filter. Diorama & Accelerated Evolution don't sound the same, but they're kind of conceptual and ideological cousins.
Obviously, Opeth are closer to DTB in the loud guitar department, especially on Blackwater Park and Ghost Reveries.
And you just can't go past Porcupine Tree for, well, pretty much anything really. Every PT album I own (barring the very odd "On the Sunday of Life) is just gorgeous, perfect rainy-day music. I'm now waiting desperately for the reissues of "Stupid Dream" and "Lightbulb Sun" to be released, so I can complete my PT collection.
Recently I've started getting into instrumental progressive music. Stuff like Godspeed You Black Emperor whose songs typically last 20 minutes or more. If you've never heard them before, let me elaborate a little bit: when I say "progressive" I don't mean anything along the lines of Dream Theater or Spock's Beard or Yes. Rather, GYBE employ more of a droning, shoegazing vibe. The songs usually start out quite sparse, then gradually add small sections of instrumentation until piece by piece everything builds up into a lavish climactic explosion of beauty. I can highly recommend "Yanqui U.X.O." and "Lift Your Skinny Fists Like Antennas To Heaven". For a sample of GYBE music, watch the start of the movie 28 Days Later. There's a bit at the start of the film where the main character's walking through a completely deserted London - the soundtrack which accompanies that scene is pretty typical of Godspeed You Black Emperor build-it-up-then-burn-it-down instrumental approach.
Another band along similar lines is Explosions In The Sky and in particular their album "The Earth Is Not A Cold Dead Place". Great album, only 5 songs but all hovering around the 9-minute mark. Kind of like Sigur Ros without vocals. I've got it playing now; fuck, it's good. Probably my favourite album at the moment.
For a heavier version of Explosions In The Sky, try a band called Pelican. Less beautiful than either GYBE or EITS, more distorted ugly feedback, but just as haunting and epic.
For a heavier version of the same thing but with vocals, see Isis.
I also gotta say, despite not sounding anything like DTB and also having by far the longest album title in my iTunes library, the new Coheed And Cambria album "Good Apollo I'm Burning Star IV, Volume One: From Fear Through The Eyes Of Madness" is quite insanely, eerily good. Took a couple of listens to warm up to, but I find most really good albums are like that.
On the much heavier side of things, "Alaska" by Between The Buried And Me is pretty good. Especially the song "Selkies: The Endless Obsession" which is kind of Opeth-flavoured in parts.
And so far, the Unexpectedly Good Album Of The Year Award goes to Finch's "Say Hello To Sunshine". Don't know what it is exactly, I just really like it.
Ro