Another fine organization is SCORE, a 501 (c) 3 organization. The acronym stands for Service Corps of Retired Executives and the organization was initially started with retired persons who shared their experiences and advice. Today, you do not have to be retired to volunteer for SCORE.
SCORE provides many free services to small business owners including business plan reviews, mentoring and workshops on different topics.
Visit their website at https://www.score.org for more information.