I've only recently discovered the post-metal genre in about the last year and I've found quite a bit of stuff that I like, if you haven't heard them yet try Red Sparowes, Russian Circles, and Pelican all of which are instrumental, and then of course there's Isis, Rosetta, Intronaut, MilanKu, OM and Old Man Gloom to name a few.
Another band, not really post-metal, just a band that for some reason I think you'd like is S