Probably not as high as you think. Indy Racing is barely staying above water. Danica is the only big money maker in Indy Car. Read the August, 2008 issue of Car and Driver. They talk about the financial dealings of Champ Car and Indy Car. The big money is in NASCAR and F1.
The most famous Indy 500 driver named Al are Al Unser Sr and Al Unser Jr. They are father and son and both have won the Indy 500, Al Sr 4 times.
British driver Dan Wheldon .
He is an Indy Racing League driver.
Dario Franchitti. He is an Indy Car driver
Al Unser Sr.
Since the Indy Racing League (IRL) began in 1996, that is Tony Kanaan with 13 IRL wins (through the 2009 season) but no Indy 500 win.
Scott Dixon has 21 wins