The PS3/Vita platformer Knytt Underground is available on PSN, promising grand subterranean adventure and "zen-like gameplay." It's Cross-Buy, so if you get it one platform, you have it on both.
Also on PSN this week: a lot of discounts! The Holiday Essentials sale is accompanied by other discounts, including the "Sega Heritage Collection" bundle, which offers Jet Set Radio HD, Sonic Adventure 2 with DLC, and NiGHTS for $20. Check the PlayStation Blog for a rather extensive list of deals. You can pre-order PSN versions of Devil May Cry and Metro Last Light starting this week.
A trio of Rockstar PS2 games is also on the Store today, for $10 each: Red Dead Revolver, Bully, and Midnight Club 3 Dub Edition Remix.