Go to the main menu, click options, and then click Cheats.

Password - Effect

needaride - All decks except for the Inkblot deck and Gamestop deck will be unlocked and free.
yougotitall - All specials unlocked in the shop
drinkup - Full Air Stats
birdhouse - Inkblot deck
newshound - Skate as Anchorman
hohohosoi - Skate as Christian Hosoi
militarymen - Skate as Colonel and Security Guard
strangefellows - Skate as Dad and Skater Jam Kid
notmono - Skate as Jason Lee
mixitup - Skate as Kevin Staab
manineedadate - Skate as Mascot
wearelosers - Skate as Nerd and Bum
shescaresme - Skate as Pat the Realtor
themedia - Skate as Photo Girl and Filmer
enterandwin - Skate as the Grim Reaper
plus44 - Skate as Travis Barker
badverybad - Skate as Twin
suckstobedead - Skate as Zombie Officer Dick
hatedandproud - Vans No Skool Gothic shoes