Aasimar after a brief period of being allowed during the year of the demon proved to be a little TOO Popular and were put back on a restricted basis. (Overpopulation AND an invasive species from another plane? A druids work is never done..) You can still come accross a boon (special certification) for them on occasion though.
Allowed races are the core rules,
Eastern (Nagaji (snake people), Kitsune (fox people), Wayang (shadow puppet people), and Tengu (Crow/Raven people)
Elemental (Oread, slyph, ondine, ifirt)
I put together a briefer guide than the official guide here