Just noticed the new realignment for Nebraska schools for 2012-2014.
Looks like there will be 14 schools competing in sixman for the next cycle there; they show 114 playing 8 man (two divisions). They also have a link at their site to a group called the "Nebraska Six Man Football League, which takes you to an eteamz.com site. From what I gather, the 8 man leagues are actually part of the Nebraska School Activities Association (their version of UIL) and the sixman league may be an independent group.
Nebraska allows schools to "coop", which means two schools can join together for athletic purposes. In fact, one of the 14 sixman schools is a "coop," (Elba/North Loup-Scotia). It looks like several former sixman schools in 2011 elected to "coop" with other schools and play 8 man (Lynch, Wheeler Central, Arnold, Loup County), while Greeley-Wolhbach and Cedar Rapids 'coop"-ed together to form an 8 man squad. South Platte went from 6 to 8 man.
I think they had 17 schools last year; I noticed a couple had gone co-op and to 8 man; the sixman league talks about games with Wyoming schools (perhaps an all-star game), which I believe sanctions 6 man play and a state title.
Schools are listed on the classification link (six man schools on page 7)
There is also a link to the sixman league there.
Also, Colorado will probably be announcing their alignments in the next couple weeks; some schools are expected to move between 6 and 8 man districts.