I have never write a driver.
Can any guy introduce me some forums ?
Thx a lot!

Any particular reason?

Do you have a network card that doesn't have an existing driver or do you just want a challenge?

You could take a look at Ndiswrapper which will allow you to use the existing windows driver under linux.

I want to write a drive for wnic so that the card can send any packet I want to send.

thx

Among the 3 class of drivers, I would say that the network drivers are the hardest to code/debug but if you're really interested, have a look here:

http://lwn.net/images/pdf/LDD3/ch17.pdf
http://lwn.net/images/pdf/LDD3/

If its for Linux 2.0,2.2,2.4 then you probably should look here:
http://www.xml.com/ldd/chapter/book/ch14.html
I used this one to code a network driver, there is some information but it's not sufficent. You can also look directly at the kernel source (the best documentation)

In any case, you will need information for your chipset : registrer, GPIO,... which is not always available and then there is no luck

Happy coding