I've always wanted to do more to "change the world", but I've found that I am ineffective/unmotivated to do so through direct actions via volunteering. I've tried and I'm not good at it. My wife and I used to have many discussions about this (she's much better at the direct help actions than me).

After I had a nice startup exit in 2001, I found that I could try to change the world (or at least things I can see around me) much better through directed donations and angel investing. That lets me broaden my effect without doing the parts that I am not good at doing. I still like the startup game too. :)