I understand that n900 is armel, but tegra 2 is ARM. Is there anyway to run armel stuff chrooted in arm environment? I would love to have maemo on my tablet. I tried to chroot into rootfs from firmware bin file, but it fails. (obviously) How hard is to port from ARMEL to ARM? Is simple recompile for correct architecture would be enough? Also, what parts(source) of Maemo are available to us?

Google is not really helpful with armel -> arm chroot.

You don't say what your "environment" is, but In short: yes, and you probably don't even need to chroot. The term "armel" refers simply to ARM in little-endian mode (the ARM architecture is bi-endian).

Are you saying that arm cpus can support both modes (same chip)?

YES it is so.

An ARM Cpu can work in Big Endian and in Little Endian.
On some recent ARM cpu you can choose/change the desired mode with a control bit on cpu's status register while on more older ARM Cpu the endianness of system is determined by circuitry that connects cpu to its peripheral components