In no particular order...
 
 

The House of Mouse	General mouse info; Mouse FAQ, mouse pictures, even mouse postcards!
Turnbaugh Homepage	Mouse breeder; hairless mice; mouse varieties.
Mice R Nice	Mouse breeder, pictures.
Gerbil's Place: Mouse Page	Mouse pictures, information etc.
Keyboard's Mousery	Mouse stuff.

 

Mischeif 'N' Mayhems Mouse Page	Mouse breeder, OH.
RMCA Homepage	Rat & Mouse Club of America's site.  More links 'n' stuff.
AFRMA Homepage	American Fancy Rat and Mouse Association.  Mouse standards, varieties, pictures 'n' stuff.
Myomorpha	Mouse breeder and rescuer, IL.
GLRMCA Homepage	Great Lakes chapter of the RMCA.

 

Mouse FAQ	Just that; a mouse FAQ.  Of course.
Finnmouse's Site	A finland mouse club, but includes information that's good for anybody!  Breeding, exotic mice, genetics etc.