My son (now 8) got the coolest airplane building kit for Christmas -- he loves it.
Boys are either "into" legos or not. Mine's not and he HATES when he gets Legos as a gift.
Here's what my 8.5 year old like right now:
Magic 8 Ball
Etch A Sketch
A Mario T-shirt.
Sports equipment of any kind.
Baseball-football-hockey trading cards
DS or Wii games or Game Stop gift card
If he likes games:
Apples To Apples