The blog page i.MX6 boards collects known i.MX6 boards. Please have a look there if you are interested in a i.MX6 board. And please add there missing boards.
For Linux, there are several SW resources:
Timesys has partnered with Boundary Devices and Freescale to provide Linux BSP/SDK for Nitrogen/SabreLite i.MX6 boards. More info on BSPs/SDKs here. This includes access to uboot, Linux kernel, toolchain and many tools/APIs for the filesystem together with docs.
We've moved the Boundary Devices git trees to GitHub.
Notes are here:
http://boundarydevices.com/git-repositories-have-moved-to-github/