According to a site which was translated from Spanish into English so we could read what those buggers were saying, Sony has just released a white papaer which contains a list! Sony Computer Entertainment confirms on that list that Ratchet & Clank: Size Matters, a PSP game just released over a year ago, will be ported to the Playstation 2. While I cant vouch for the game as I dont have it for the PSP, the Ratchet & Clank series is absoutely good fun especially with Ratchet & Clank: Tools of Destruction for the Playstation 3.
Many people are arguing on the site as well that this could also open the way for a port for the PSP game, Daxter, a spin-off of the Jak & Daxter series for the PS2 which would be great news considering everybody loves Jak and Daxter.
Anyways, the R&C port for the PS2 is apparently due out in Europe on March 19th.