Ok completely new update, the other one got confusing so I'll just delete it. All of them have improved since the last update except for Mushroom Gorge I believe (I should really start using that shortcut :P)
(Updated as of October 12, 2009)
Luigi Circuit- 1:10.840
Moo Moo Meadows- 1:19.975
Mushroom Gorge- 1:53.556
Toad's Factory- 1:58.452
Mario Circuit- 1:25.181 (You just had to beat me by 1/10th of a second, didn't you TWRo0 :P lol)
Coconut Mall- 2:03.593
DK Summit- 2:01.560
Wario's Gold Mine- 1:59.451
Daisy Circuit- 1:33.602
Koopa Cape- 2:29.672
Maple Treeway- 2:26.294
Dry Dry Ruins- 2:06.602
Moonview Highway- 1:51.562
Bowser's Castle- 2:32.957
Rainbow Road- 2:37.437
GCN Peach Beach- 1:17.952
DS Yoshi Falls- 1:03.573
SNES Ghost Valley 2- 56.494
N64 Mario Raceway- 1:45.821
N64 Sherbet Land- 2:12.465
GBA Shy Shy Beach- 1:28.310
DS Delfino Square- 2:10.401
GCN Waluigi Stadium- 2:06.074
Desert Hills- 1:45.063
GBA Bowser Castle 3- 2:17.193
N64 DK's Jungle Parkway- 2:20.305
GCN Mario Circuit- 1:37.403
SNES Mario Circuit 3- 1:21.789
DS Peach Gardens- 2:07.427
GCN DK Mountain – 2:22.031
N64 Bowsers's Castle- 2:42.041
