The American Marketing Association – Baltimore Chapter
http://baltimore.marketingpower.com/
Baltimore’s local chapter of the American Marketing Association has more than 450 members, making it one of the largest in the country. There are numerous volunteer, networking and social events, as well as educational programs and presentations to enhance members’ marketing skills. Membership includes a subscription to Marketing News.

Association of Information Technology Professionals (AITP) -- Baltimore Chapter
http://www.baltimore.aitp.org/
AITP Baltimore’s purpose is to promote professional development and industry leadership among its members. It organizes networking and business development programs, and provides financial and legal services. The group has been meeting since 1951 and currently has more than 100 members. Membership costs $140 per year.

AITP – Baltimore Chapter
P.O. Box 17598, #65102
Baltimore, MD 21297-1598
Email: getinfo@baltimoreaitp.org

This is just a sample of what you'll find in the complete Baltimore guide.