From left to right:
Broon Jr -- Dressing as his favorite Renaissance performer, Broon. Among other things, Broon eats fire.
Marvin the Martian -- One of two costumes with a broom on his head. More pictures here.
Pumpkin -- His first costume, not homemade.
Alvin the chipmunk -- Way before the movies came out.
Peter Pan -- Alas, this boy does grow up.
Pinocchio -- Worn at Disney World a year where we spent Halloween there.
Peter Pan again -- A new version of the costume, also from a year we were at Disney World.
Wee ghost -- Briefly worn at bedtime after setting up the black lights the day before halloween.
Danny Phantom -- Socks worn OVER the shoes as cheap white boots for the win!
Bobba Fet -- Not really a full costume, but this picture was shot at Disney World near halloween.
The Blue Spirit -- Character from the "Avatar: the Last Airbender" TV show. Papier-mâché mask. More pictures, including the build process of the mask can be seen here.
Jedi -- No one in particular, but in the style worn by Obi-wan and Qui-gon. More pictures here.
Dr. Horrible -- Doctor Horrible from the end of "Dr. Horrible's Sing-Along Blog". Lots more pictures here.
Tenth Doctor -- The tenth Doctor from Doctor Who, our family's favorite doctor.
Roman soldier in the cardboard legion doing battle with wild cats-- Taken from this instructable, more pictures are available here. The other costume incorporating a broom on his head. This got him a 100% grade in Latin class a few days ago.
Not shown (But will be added if the pictures turn up):
A batman costume from a year the "only homemade costumes" rule was broken.