He's being charged with abuse of power and coercion stemming from an ethics inquiry over his veto of a public integrity unit. If anything comes from this, it could have ramifications for the TX-Gov race between Wendy Davis and Greg Abbott. It will certainly have ramifications for Perry's hypothetical run for the presidency in 2016.
4:09 PM PT: He's been presented with two felony charges:
1) Misuse of government property - preventing funding of Texas' Public Integrity Unit
2) Coercion of government employee Rosemary Lehmberg after she was charged with a DWI. Perry wanted her to resign.
(h/t to jayden in the comments)