I have a couple hundred or so. I live just a few miles from Michigan Intl. Speedway, and take a lot of photos at the track, so there are a lot of opportunities to get some nice 8 x 10's , books, or vintage programs autographed. Even better than the autograph, you get the opportunity to take a few minutes to speak with your heroes.
For example, on one IRL weekend I got Rick Mears, Gordon Johncock, Bobby Unser, Al Unser Sr., Johnny Rutherford, and AJ Foyt. I am a big Indy 500 fan, so a lot of others besides the ones I mentioned like Lloyd Ruby, Jaanet Guthrie, Lynn St James,Helio, Hornish, Franchitti, Danica, Weldon, Lazier, Marco, Mario, Dixon, Kanaan etc.
Ford had an awesome event at Greenfield Village in 2001 to celebrate their 100th anniversary in racing. At that one event I got different racing books in my collection signed by Dan Gurney, Parnelli Jones, George Follmer, Carroll Shelby, Jackie Stewart, Junior Johnson, Ned Jarrett, and the Wood Brothers.
As far as NASCAR goes, most of the all time greats like Richard Petty, Rex White, David Pearson, Bobby Allison, Mark Martin, Dale Earnhardt Sr., Dale Jarrett, Bill Elliott, Ken Schrader, Tony Stewart, and many of the other current drivers as well. I got to meet Richard Petty one time at an airport when we were on the same flight and the plane was delayed; spoke with him and his wife for 20 minutes or so.
Then dozens of retired and active short track sprint and stock cars stars as well.
I actually don't really go out of my way to get autographs at the track ; if there is an opportunity to get one of my favorites at an appearance or something, I will take something cool with me, but I'm not out there trying to chase them down like many fans I see at MIS.