Last one was '04 at Milwaukee for me. Dario Franchitti won. We actually went to see the USAC Silver Crown and Midget races the day before and went back for the IndyCars. I really do not wish to spend the $$$ on going anymore. The local dirt scene is more than good enough for me.
However.... I do remember my first IndyCar race very well. Having followed NASCAR for decades (let me finish before you go berserk) and religiously going to the MIS races in the infield, my friend and I decided to go check out the CART race one year. 1994. It was about 95⁰F out. We took a big cooler of beer with us, parked, and started walking towards the tunnel. We were told time after time, "You can't take that huge cooler in there."
Our repeated response was, "We are going in the infield," followed by many confused looks from fans.
Well, we walk into the infield, plop down in Turn 2, and unlike a NASCAR race, the infield is barren. Only a few fans around the perimeter from Turn 2 to Turn 3. No wonder the majority had no idea about the infield cooler policy. No one was in it.
The race starts and the cars come through Turn 2 for the first lap. MAN were they fast! I take a sip, look around, and in what seemed a blink of an eye, ZOOOOOM..... they were going past us again!

Took about HALF the time the stock cars took to come around.
The true sense of speed was an incredible rush. And the lack of noise (turbo era).
It is one thing zipping down a straightaway to 200+ mph. Seeing it through a high banked corner like MIS was another level of rush. Alex Zanardi took honors that day in a Ganassi car.
Sure do miss MIS on the schedule. If they came back, I could probably be talked back in to going again. Until then..... T.V.
Good topic, Rich. Thanks for starting it.