I think I'm like many others here where I haven't done some fast, extreme switch but rather my ideas and opinions have evolved over the years. I didn't have strong opinions when I was younger and I've gotten a little more certain about some of them, and in social issues I have definitely grown more strongly liberal.
Many people are mentioning religion here. I was raised in a theist household, I've gone through periods where I experimented with atheism, and these days I'm a pretty comfortable theist.
Growing up I had a narrower view of not just myself but also what my life would be like. I thought I had to follow a specific script and was always really hard on myself when I failed to. These days I'm reasonably comfortable with the fact that life can change in an instant. While I'm sure there are many challenges ahead, I don't have such strict expectations for myself. I think this attitude made it easier to deal with my marriage ending because I didn't instantly go into "My life is over" mode.
The area with the most extreme change would be just being less judgmental in general. I think that posting on internet forums is directly involved in that. In real life I tend to hang out with a more conservative group of people and we can often be superficial. Meeting people online opened up my social interactions with groups that I would never have really crossed paths with in real life. As a result, I found my own opinions changing but also I sometimes say things in real life now when someone mocks someone else. I probably don't speak up as much as I should, but I'll get there. I think it's a good improvement and it just feels right to me, to be more understanding and less judgmental.