StreetPass Squad - Developer: Good-Feel (Kirby's Epic Yarn, Yoshi Yarn)
-The game is a shmup in which StreetPasses can be collected as weapon power-ups in each stage.
StreetPass Garden - Developer: GREZZO (Ocarina of Time 3D, Four Swords DSiWare)
-The game is a slow-paced gardening game in which StreetPasses not only water your flower to grow, they also bring their own flower to display. Grow them all!
StreetPass Battle - Developer: Spike Chunsoft (Pokemon Mystery Dungeon)
-The game is a battle game based in older Japan times. It looks like the StreetPasses you make join your clan with all of their streetpasses as their armymen. Fight against enemies in Paper-Rock-Scissors style plus your army count.
StreetPass Mansion - Developer: PROPE (Ivy the Kiwi, Let's Tap, Wii Play: Motion's Trigger Twist)
-The game is a combination of a puzzle-adventure and exploration adventure. StreetPasses give you maps which allow you to add rooms to the mansion and potentially find items. If you encounter ghosts, this initiates a battle sequence with the items you've collected.
All of them look quite good, actually!