Some good webpages and sites about engineering?

[Edge]

Which are some good pages about applied science and engineering?

 

I'm looking specifically for pages about hydraulics, thermodynamics, electronics, circuits and physics in general.

 

Because some times I have trouble finding definitions of some things and other kind of info. That's why I ask.

 

So, which sites are good in your opinion for this?

 

Thanks.

[teguy5]

efunda

[GeneralMotors]

any good portals on wikipedia?