The British Gaming Blog has a complete list of the tracks in the upcoming Mario Kart DS title. There's eight unlockable characters, too. Get!

Tracks after the fold.
Mario Kart DS - Full Track List [British Gaming Blog]

Retro Mode

Shell Cup
Mario Circuit 1 - Super Nintendo
Moo Moo Farm - N64
Peach Circuit - Game Boy Advance
Luigi Circuit - GameCube

Banana Cup
Donut Plains 1 - Super Nintendo
Frappe Snowland - N64
Bowser Castle 2 - Game Boy Advance
Baby Park - GameCube

Leaf Cup
Koopa Beach 2 - Super Nintendo
Choco Mountain - N64
Luigi Circuit - Game Boy Advance
Mushroom Bridge - GameCube

Lightning Cup
Choco Island 2 - Super Nintendo
Banshee Boardwalk - N64
Sky Garden - Game Boy Advance
Yoshi Circuit - GameCube

Nitro Mode

Mushroom Cup
Figure-8 Circuit
Yoshi Falls
Cheep Cheep Beach
Luigi s Mansion

Flower Cup
Desert Hills
Delfino Square
Waluigi Pinball
Shroom Ridge

Star Cup
DK Pass
Tick-Tock Clock
Mario Circuit
Airship Fortress

Special Cup
Wario Stadium
Peach Gardens
Bowser Castle
Rainbow Road