I'm not sure if I've experienced any overt ageism. If I have I certainly didn't notice it.
An interesting thing did happen to me just last week though - the interesting part being my reaction to a simple question. As a little background, I'm the second or third oldest employee in my workplace. The three of us putting the drag on the actuarial table for medical insurance rates are probably at least 15 years older than the next cohort of employees and it gets younger from there.
There were three of us working in a shared office space. The other two were working while also talking about possibly returning to school. One of these employees is 35 and the other probably 23. The 35 year old said that they didn't feel like they were good at anything. The youngest said something along the lines of "maybe it just takes awhile to figure out what you're good at." Then they turned to me and said, "Dan, how old are you? Do you feel like you're good at things? When did that start?" I don't think the age question was asked with any malice, subterfuge or any other nefarious reason behind it. If anything the recognition of a difference in ages while soliciting my opinion showed that they valued my age, whatever it may be. Implied in the question was the assumption that I had some different perspective to offer, and that arose from a greater breadth of experiences.
So for all of that, I balked at saying my age. I just said, "I'm certainly older than 35," and then went on to answer the other questions. I was actually taken off guard by my own response. I'm certainly not ashamed of my age. I also didn't (and still don't) think that answering the question would've harmed my career there in any way. I value my working relationship with these coworkers, and I think I was worried that stating my age, 57, would change that relationship in a negative way. It's quite possible that I'm older than the youngest one's father, and I could be the same age as the older one's. That's not very likely, but still possible. So somewhere in the back of my mind was the worry that knowing my age would change the way they saw me and/or interacted with me. "Whoa, you're older than my dad. Let me get you a wheelchair." But that's not really giving my coworkers the benefit of the doubt.
I've worked in organizations that had a real rat race vibe or culture. This one isn't one of those at all. The fact of the matter is I expect I'm not nearly as cool or hip as I think I am, and they've probably already pegged me as around ten years younger than the president. I guess the moral of this story is that I didn't experience ageism at that instant, but rather let a fear of ageism control my response.