Using Extensions?

I want to try using Multitexturing in one of my codes but the only way I found to do this is by using extensions.

Can anyone explain how to use extensions or post links to sites that explains them.

Thanks!

Yeah, I would like such info also!

NeHe has some excellent tutorials http://nehe.gamedev.net/ one specifically talks about multitexturing

i dont really explain them but ive got a few examples on my site http://members.nbci.com/myBollux stuck up a new one last night seperate specular colour (very unexciting)
mark kilguard has written a good article on extensions a link is on this sites home page