As the site becomes bigger it's reasonable to suppose that contributors will have asked, answered or commented on various questions scattered all over the site. It would be nice if there could some way to keep track of all these, perhaps an optional link section on each user's profile page to those questions they have asked or responded to? This would make it much easier to revisit these questions at a later date.
Currently, if you click on a user's name it takes you to their profile which contains exactly what you're describing for questions asked and answers given. If you then click on the user's "activity tab" you can see a stream of their activity, including comments.
Additionally, for every question, if you look in the lower portion of the right hand column there are the associated tags, when it was asked, how many times it's been viewed, if there are any linked questions, the list of linked questions, and finishing out that column is any questions the stackexchange system thinks are related.