Swarm and PSP's Hoard. If you haven't checked out the demo from last week's PSN exclusive Slam Bolt Scrappers, that's definitely worth taking for a test drive.
For something with a bit more machismo, the demo for WWE All Stars is available, along with Castlevania: Lords of Shadow's "Reverie" DLC. Konami kinda just snuck that release in this week for the States, but it should be available in Europe on March 30.
There's plenty more to peruse in the full update after the break.
Choose your platform to view the corresponding release list:
(Note: Continue past the break to view both release lists.)