After looking for more than an hour to find an easy to use, hopefully ad and virus free avatar creation site, the best I’ve found is https://avatarmaker.com.

It’s easy, fast and free. It even allows to upload your newly created avatar directly to Gravatar.

Only handicap is that it does not allow you to create an avatar from a photo, buy anyway I did not find any free easy to use site that creates avatars from pics.