Helping those who are unemployed, who would like to transition into another career, or individuals who are just trying to find their way. I got some of the info from http://oprahsangelnetwork.org.

If you are are starting a business or have already started one and want a business mentor visit
Micromentor: http://www.micromentor.com

If you are looking to utilize your skills to help others or want to learn new skills, volunteer! To find volunteer opportunities in your area

Volunteer Match http://www.volunteermatch.org

Or if you want to organize volunteers for a project you're working on

Hands On Network http://www.behandson.org

For individuals 25 years or younger
Do Something http://www.dosomething.org

Have you always wanted to learn a language or take classes but haven't had the time or finances?

36 Language Lessons FREE!
BBC http://www.bbc.co.uk

For non-degree, non-accredited, non-certificate courses
MIT (One of the best) http://ocw.mit.edu
UC Berkeley http://webcast.berkeley.edu
Yale http://oyc.yale.edu
Stanford http://itunes.stanford.edu or just log on to itunes store and type in Stanford University (less info)