Select the Special option from the main menu, then choose Cheats before entering following codes:

Big Head Mode:

At the Cheat menu enter code DULUX

Level Select:

At the Cheat menu enter code XCLSIOR

Infinite Web:

At the Cheat menu enter code STRUDL

Spidey's Special Armor:

Watch for a gold spider icon during the Venom chase, grab it to gain Spidey's Special Armor.

Invincibility:

At the Cheat menu enter code RUSTCRST

Full health:
At the Cheat menu enter code DCSTUR

All comic books:
At the Cheat menu enter code ALLSIXCC

Amazing Bagman costume:
At the Cheat menu enter code AMZBGMAN

Unlock everything:

At the Cheat menu enter code EEL_NATS

Debug mode:
At the Cheat menu enter code LLADNEK

All characters in viewer:
At the Cheat menu enter code CVIEW_EM

Storyboard viewer:
At the Cheat menu enter code CGOSSETT

All movies:
At the Cheat menu enter code WATCH_EM

BNREILY:

Get Ben Reilly costume

GBHSRSPM:

Makes the story unfold differently, for example when you find the Black Cat in Doc Ocks secret lab, she is go-go dancing, some differences are small buts some are big.

PARALLEL:

Spider-Man unlimited costume

TWNTYNDN:

Spider-Man 2099 costume

BLKSPIDR:
Symbiote costume

S_COSMIC:

Captain universe costume

MJS_STUD:
Peter Parker costume

RULUR:
J James Hewitt character in character viewer {head of Neversoft the guys who made the game}

ALMSTPKR:

Quick change costume

LLADNEK:
Debug mode

LETTER_S:

Scarlet Spidey outfit