They issued a double cd last year that is a compilation of pretty much everything Tarkio ever put out, it's called Omnibus.
I highly recommend checking it out if you like the Decemberists. It has a more rootsy feel, with some songs even having an alt-country feel, and it fucking roolz. Still weird and strange songs with bizarre content, but if you are into the Decemberists, you are probably into the freaky shit. ;)
Anyways, give 'em a listen.