Hey guys, I have the 24" iMac.
I remember seeing a video on cnet about how they can connect one MacBook to the internet via ethernet cable, and then it would provide WiFi for other.
Is it the same on a iMac? If so, how would one do that?
Yep it is exactly the same. You need to go to system preferences, and select sharing, then internet sharing, and set up to share your ethernet to your AirPort.