Mentors come in two flavours - official and unofficial. An official mentor is part of a formal agreement and may even be regulated by your employer, and an unofficial one is someone you adopt and turn to for advice; I have one of each.
My offical mentor is Lig. my "Big Sis" from phpwomen.org where we run a Big Sis, Little Sis scheme. I expected this to involve a lot of technical input but the biggest thing I've got out of this relationship is moral support and an introduction to the wider php community - who in turn provide more of the aforementioned moral support in addition to the raft of technical information you'd expect, and serveral more rafts that you wouldn't!
My unofficial mentor Mark is an ex-colleague from Snowdrop. Whilst we've only met a handful of times in person I took over the Oracle DBA stuff at Snowdrop from Mark and spent a lot of time on the phone/jabber/email with him with that and various other projects. Although we're both now working elsewhere, live far away from one another, and have other distractions in our lives we still stay in touch. Mark is my "professional" mentor - although we work in different fields of technology, I tap into his business experiences to inform my own choices and deal with situations that are new.
Models are people whose behaviour you learn from or emulate in order to extend your own skill set, either by being actively coached by that person or by learning by observation. I have learned from a senior manager that to stutter endearingly while delivering bad news can work surprisingly well (not an approach to use every day!). When I worked as an administrational temp one summer, I was told to smile when on the phone - something which came in very handy when I worked on a technical helpdesk a few years later. I've also learned numerous tricks and techniques from the old hands in the technical departments in the various places that I've worked. These battle-hardened geeks can be hard nuts to crack, but they have so many stories to tell its worth it - and some have grown to be real-life friends.
Sometimes you have to ask to be taught something, this can be tricky to do if the person is busy or you are shy. On other occasions you may be able to learn from observation or the other person may mentor you of their own accord. However it happens, I try to make the most of the positive role models and coaches around me. From these people I have learned so many of the skills that I use day-to-day to perform my role and I'm grateful!