Yesterday's firmware update allows a workaround to gain more than the few PlayStation 1 games that were promised for the PS Vita. While Europe was getting 129 games and Japan was getting over 200, this is something that can be done, but at your own risk. The extra titles had not yet gone through Sony's quality control.
Joystiq informs us that "NeoGAF has a users-confirmed list of PSOne games that can be transferred using the PS3, and those that can be downloaded from the Vita store as well (in bold). "
Here is the list, followed by the YouTube user, FistFullofPotions, who found the way to transfer the games:
2 Xtreme
Alundra
Arc the Lad
Arc the Lad II
Arcade Hits: Shienryu
Arcade Hits: Sonic Wings Special
Bowling
Breath of Fire IV
Castlevania
...