From: eLinux.org
Tegra 2 is a system-on-a-chip (SoC) created by NVIDIA. The SoC comprises a dual-core ARM Cortex-A9 with FPU per core, an NVIDIA ultra low power (ULP) GPU, an embedded ARM7TDMI and five other processing cores for audio and video processing.
The NVIDIA developer zone has more information on Tegra.
There are forums for software developers and the like.
[TODO: Add information about dev kit hardware]