Many email clients allow you to get email from multiple email servers. As has been mentioned by several, Gmail is one of them and that is what I use. I've never used AOL, but I have set several friends that have up with Gmail and they get their gmail as well as their AOL mail in gmail. Try it, you will like it.
I have eight email addresses that I use or monitor and all come into my Gmail. When you get an email in gmail, if you reply to it gmail puts the original email address as the sender so the sender sees a response email from the same email address as they sent it to.