You might have read yesterday that the PlayStation Vita's PS Store is now officially online and ready to accept your money. The current offering of actual Vita games is relatively light, but there are hundreds of PSP and Minis titles available for purchase and/or download. The exact number is 275, Sony reveals in a new PlayStation Blog post.
The update explains the various options users have for getting a PSP onto your Vita's memory card. It's pretty simple, really: either download them straight to the Vita via the built-in PS Store app or download them to your PS3 and then transfer them over using the Content Manager. You can find the full list of games at the source link below, though I can also confirm that LittleBigPlanet PSP, Killzone: Liberation and Echochrome can all be transferred from your PS3 to the Vita as well, and that they all seem to run just fine.
Sony promises to add more PSP titles to the store "in the coming weeks."
Source: PlayStation Blog