New Math - Drive Like Jehu
Nosferatu Man - Slint (5/4? Neat song.)
Republic of Rough and Ready - Hella
Glasgow Mega-Snake - Mogwai (basically 6/4, with 5/4 bits? Or it just skips.)
Focus on A Roller Coaster - Mice Parade
No One Likes a Grumpy Cripple - Rumah Sakit (7/4 and 6/4?)
And Giraffe, Natural Enemies - OXES
Cornpone Brunch - Tortoise (basically 6/4?)
Breadcrumb Trail - Slint (7/4)
Nasty Portion - Sleeping People
*to be updated as I listen - "math rock" tag radio and several other stations.
Darkmatter - Porcupine Tree (7/4) *via neighbourhood radio
LUH - Isotope 217 (seven)
Spooks The Horse - Youthmovie Soundtrack Strategies (seven, five, seven, five, ... three or six, ... seven, five ... or something. very complicated. via recommended radio)
I forgot to mention And So I Watch You From Afar. They've got several 'irregular' songs, and their music is just awesomely beautiful.