Where do I find out all the motherboards that are supported by a particular version of linux.
Or specifically Centos 5?

That would be a hardware compatibility list (HCL). There used to be a few central ones on the 'net and we have one at LQ. Compatibility (except some device support) is not related to a distribution but to the kernel. Depending on how exotic the hardware components are and how much developers and supporters joined in to make it work you may or may not find clues on the LKML, changelog, $kernelversion/Documentation and kernel source.

You can check buyers reviews at Newegg and such. Often times they will mention linux.

I remember reading somewhere that linux actually have all the drivers for the motherboards inside it so users do not need to install drivers for their motherboards.

If a major manufacturer comes out a new chipset, is the current lastest linux kernel able to support it?

@khaos83:
Of course! Any new chipset will instantly be recognised by the latest linux kernel.

This is because the linux kernel developers know in advance what the chipset specifications will be, without the manufacturers needing to provide any information at all! That's why manufacturers usually don't provide information: It's only "windows" that needs "drivers".

Think about it

I am amazed at the hardware I can plug into my linux systems, and it "just works". No drivers to load, no lengthy "Licence Agreement" to read (you did read that windows thing, didn't you, before you clicked [Yes]? Every word of it? Do you understand what you are accepting actually means?)

One of these days I am going to write a windows program with all the usual "Read the licence"... "Accept the licence".. Click [Yes] to accept the licence.

And they will.

Without having read my licence, which says, amongst many other things: "After 42 days, you agree to give me your house, car and money. You agree that this is not contestable in any court of law anywhere in the world, because you have clicked [Yes]"

Looks like I get to retire early : $£$£

So to the reality: "If a major manufacturer comes out a new chipset", then it'll probably be quite some time before some poor light-deprived hacker manages to work out exactly what bytes need to be passed to the chipset to make it work, and then works out exactly what to do with the data that is returned. And then publishes his work for us all to enjoy, and be thankful for.

Get real

Here is a great place to read linux hardware reviews. They test the latest hardware and discuss linux compatibility and performance:
http://www.phoronix.com/scan.php?page=home