Every PS2 CLASSICS game on the PlayStation Store (EU) - YouTube
How To Find ALL PS1 / PS2 / VITA Games on the PS3 Network! EASY - YouTube
Castlevania titles are part of this weekend's PlayStation Store Flash Sale! Five titles with the sales being 50% to 75% off! PS3 PSP & Vita : r/castlevania
PSOne Classics Buyer's Guide -- PS3/PSP Store Apocalypse Edition - Hey Poor Player
Here's how you can buy older, unlisted games on the PlayStation Store | Eurogamer.net
Resident Evil Director's Cut and more PS1 classics playable on PS4/PS5
Joystiq Guide: PSone downloads hit the PSP (by way of the PS3) | Engadget