which airlines today carry internet service how do you use it from your laptop?

as far as i know there are no airlines offering internet service
however they do offer a linkup either by phone or sattelite to your
own provider. usually at a hefty pricetag. what you need is a computer
with a net work card or modem dependng on the connection type offered
and a conecting cable you can usually get from the airplane attendant

ElAl provides some sort of Wi-Fi internet access

http://www.elal.co.il/default.asp?V_DOC_ID=3733&V_LANG_ID=0

How do I connect to the Internet?
To enable Internet access, you must set up your computer, sign up for
the Connexion by Boeing service, and then sign in. Once signed in,
your browser window will show your status as ?Connected to the
Internet.? Our small Status-Connexion window will open to give you a
way to access the Home page in order to check your connection status
and sign out of our service. We suggest that you leave this small
window open until you are ready to sign out.

How do I set up my computer to work with the Connexion by Boeing
service? Step-by-step instructions may be found in your in-flight
magazine or other seatback material. Some airlines offer our separate
Setup Guide instead. Your flight attendant will be able to tell you
what material is available onboard your flight.

http://www.connexionbyboeing.com/

Right now, only Scandinavian Airlines, Japan Airlines, All Nippon
Airways, and Lufhansa offer somewhat spotty Internet access on their
flights.