These are the websites I think every Maxima owner should go to.
I've been to all of these sites, and they are all very credible. I have purchased stuff from some and I'll probably purchase something from them all, and break my pockets.

For those who are unfamiliar this is a 5th gen Maxima.

These guys will make your Max faster
Warp Speed They specialize in Y-pipes that are high quality and friendly to your pockets, they also manufacture Cold Air Intakes.
Cattman Perfromance This guy has it all including Y-pipes,engine mounts, Cold Air Intakes, Strut Bars and the list goes on.
Shox Suspension, Suspension, Suspension!!!
They carry, Tociko,Eibach,H&R,and many other brand name shocks,struts, and springs for our cars.
Southwest auto This site has suspension and lighting mods for our cars......and Alex is the damn man, he'll definetly take care of you.( I got my springs from these guys)

Favorite Sites

The best damn Maxima club on earth!! This were you go to find out anything you need to know about your maxima no matter what year it is........ a large number of extremely knowlegable Ladies and Gentlemen who are always willing to help.
Courtesy they carry strut bars, pop chargers, and all of the necessary genuine nissan parts for all of you maintinence needs
JWT ECU upgrades, cams, pop chargers,etc.
digital racing Nice site that I discovered today.