Sony has published a list of 262 games which will be included in the UMD Passport scheme.
The scheme lets users register their UMD copy of owned games in order to be eligible for a discounted digital version, which will then allow the game to be playable on PS Vita. Digital versions will range in cost, from around £4-£15 depending on the title.
There are currently 606 PSP titles in Japan, so this represents a big chunk of them, with no doubt more being added once Sony can negotiate the rights with the publishers. Big name publishers currently missing from the list include Capcom, Namco Bandai, Konami and Square Enix.
As pointed out by Siliconera, you can see the entire list here.