Official RTEMS Training opportunities can be seen at http://www.rtems.com/trainingschedule.
RTEMS Training in Huntsville, Alabama is typically held once early in the year (February, March, or April) and once later in the year (September or October) at the OAR main office. Please visit the RTEMS Training page for further information and registration details.
RTEMS has always used the GNU Cross Compiler.
RTEMS has a robust set of APIs including but not limited to these modules listed below. For a complete description of the RTEMS API, see the online documentation.
The short answer is - many! RTEMS supports many different architectures. A few are listed here, but see this page for more detailed information.
RTEMS is sponsoring and exhibiting at this year's Interplanetary Small Satellite Conference. The conference will take place at the California Institute of Technology on April 28-29 in Pasadena, CA. Please stop by for more information about RTEMS.