Some great music in MIDI format, playable with Windows Media Player, WinAmp, or perhaps your browser. My personal favorites are marked with shells.

Game Theme Length File Size
The Wizard Send Me an Angel 4:01 30k
Batman Stage 1 2:10 43k
Batman Stage 2 2:23 34k
The Adventures of Bayou Billy Stage 1 1:33 36k
Blaster Master Stage 1 2:23 39k
Battletoads Stage 5 2:00 20k
Castlevania Stage 1 1:07 13k
Castlevania Stage 3 3:24 51k
Contra Stage 1 3:19 29k
Castlevania II: Simon's Quest Town Theme 1:47 19k
Double Dragon II: The Revenge Stage 1 1:38 19k
Castlevania III: Dracula's Curse Demon Seed 1:58 21k
Super Dodge Ball Stage 1 2:25 41k
Dr. Mario Chill Theme 2:06 20k
Mega Man 2 Dr. Wily Theme 1:38 13k
Fester's Quest Overworld 2:03 40k
Final Fantasy Battle Theme 2:35 47k
Golgo 13: Top Secret Episode Opening Theme 1:14 18k
The Goonies Good Enough 1:36 19k
Gradius Stage 1 2:49 34k
The Guardian Legend Area 0 Walk Theme 1:26 15k
Gyromite Level Theme 2:29 23k
Gyruss Main Theme 1:49 57k
Mega Man III Hardman Theme 1:49 12k
Mega Man VI Knightman Theme 1:51 30k
Yie Ar Kung Fu Level Theme 0:31 03k
Legacy of the Wizard Opening Theme 1:29 16k
Life Force Stage 1 0:56 18k
Metal Gear Inside Theme 1:46 23k
Metal Gear Outside Theme 1:46 23k
Mega Man III Intro Theme 2:01 37k
Ninja Gaiden Stage 1-1 1:27 18k
Ninja Gaiden Stage 2-1 1:26 16k
Mike Tyson's Punch Out!! Fighting Theme 2:25 13k
River City Ransom Boss Theme 1:38 29k
River City Ransom Main Theme 1:49 36k
Rush 'n Attack Stage 1 1:31 17k
Silver Surfer Theme 1 3:06 57k
Silver Surfer Theme 2 2:59 40k
River City Ransom Main Theme 1:49 36k
Skate or Die Opening Theme 2:45 30k
Snake's Revenge Stage 1 3:09 39k
Mega Man III Snakeman Theme 1:30 39k
Mega Man III Sparkman Theme 2:13 57k
Super C Stage 1 1:58 38k
Castlevania II: Simon's Quest Bloody Tears 1:36 22k
Teenage Mutant Ninja Turtles Opening Theme 1:07 60k
Teenage Mutant Ninja Turtles 3 Let's Go, Turtles 1:27 13k
Teenage Mutant Ninja Turtles 3 City of the Half Shell 1:27 13k
Teenage Mutant Ninja Turtles 2 Stage 1 1:25 23k
Wrecking Crew Main Theme 5:31 26k
The Legend of Zelda Overworld Theme 1:42 26k
Space Harrier (Sega Master System) Main Theme 3:58 61k