"Wan Wan Card Game" plays animal sounds, and asks players to identify which on-screen animal makes the sound. Remote Control Hide and Seek has one player hide the Wiimote, and other players find it by listening to the sounds it emits. "Sensitive Bomb" tasks players with passing the Wiimote around. If it is jostled too much, it explodes! Or, at least, probably plays an "explosion" sound effect.
According to Nintendo's release calendar, Wii Party will be out in Japan on July 8. That means it's definitely complete enough for Nintendo of America to show it at E3.