The first wave of hands-on kiosks is ready to play at Sony store locations nationwide. There you can try out games such as Knack, FIFA 14, Octodad: Dadliest Catch, Contrast, Super Motherload, and Pinball Arcade.
Don't fret if you aren't near a Sony mothership; other stores including Best Buy, GameStop, Target, and Walmart will receive their own PlayStation stations in coming weeks. Put your ZIP code in here to find your nearest PS4 sampler, but note that the "A" pins don't mean a store is there, that's just the search location (we were a little confused, ourselves).
When you do find a local kiosk, make sure you bring some hand sanitizer. Those things can get gross.