Mentoring is one form of networking. Since returning to grad school and then starting and running a research business, I have had several mentors. I've also been a mentor. In both situations, I learned more and learned it faster than I could in any classroom. I also developed some wonderful, life-long relationships with some wonderful people.
I came across an article about mentoring in the Wall Street Journal, "Your Mentor Is Out There -- in Cyberspace." It talks about leveraging the Web to make connections, but it's quick to point out that it these online connections won't "stop people from meeting in the local Starbucks."
I've mentored and I've been mentored by phone, email, and meetings at the local Starbucks. We've communicated in person, and some I've never met. In the end, it doesn't really matter how you get involved in mentoring, but do consider getting involved. It's a great way to expand your personal learning network - and meet some really cool people.