I have posted a first beta of two Real Time Operating System kernels for Teensy 3.0 as Teensy3-RTOSbeta20121116.zip Google Code Archive - Long-term storage for Google Code Project Hosting..
These systems are packaged as Arduino libraries so they can be used with other Arduino software. Since these are preemptive kernels, careful design is required to avoid problems with normally single-threaded Arduino software.
These RTOSs must be used with the beta8 version of the Teensy 3.0 software.
ChibiOS/RT is version 2.4.2 ChibiOS free embedded RTOS - ChibiOS Homepage.
FreeRTOS is version 7.3.0 http://www.freertos.org/.
Warning: If this is your first use of a RTOS, you will likely experience the pain of my bugs and problems that are inherent to preemptive RTOSs. Please read the warnings in the included html documentation.
Four examples are included with each system. These example are described in the html included with the libraries.