Yes, gmail and Yahoo! are free (and great). Yes, you get 100+ free addresses with your ISP account.
Do yourself a favor and if you haven’t already, get yourself an email addy that has your URL in it (e.g., firstname.lastname@example.org).
First, it’s yours forever for a small annual fee. No more sending out emails to your book when you switch ISPs, and far less chance of emails getting lost because people don’t know which of your 17 email addresses to reach you at.
More importantly, it’s a great way for people to find you when hyperlinks are turned off. For instance, I subscribe to a particular newsletter that that doesn’t allow URLs, but does allow email links. I don’t always want to email someone right off the bat, but I can (and do) visit the sites of contributors whose tips I enjoy by sussing out their addresses via the info after the "@" sign—something I couldn’t do with an AOL address.
Besides, it’s far better to spend your money branding yourself than AOL.