As a business development manager, what are some great, free online courses that I should be taking in order to get the most out of my online marketing efforts?

Advance Digital Marketing Course is the best way to guide you up

Digital Marketing with essence of  social Media

Digital Marketing with essence of  social media and internet trends websites 

Courses in Total Quality.

Course in Business Development and Marketing.

Course in Business Development Strategies.

To know all the Aspects of Business and especially Digital Business in todays erna and to also upgrade your skills from time to time a Business Development manager has to know the overall Digital Marketing Arena , for that you can enroll for a Free Online Course at www.digitaldeepak.com . But the process of continoue learning and tracking of the medium is very important as this medium changes day in and day out.

Most people fall in trap of online selling & marketing, which is a good thing but not the main thing. effective prospecting and effective meeting is the main key

I would recommend Mike Weinberg "New Sales Simplified" 

and if you are managing a team go for "Sales Management Simplified"

Good Luck

https://www.google.com/onlinechallenge

www.google.co.in/Online_Marketing‎

https://www.coursera.org/specializations/digital-marketing

https://www.udemy.com/online-marketing-crash-course/

As a business development manager You should focus on B2B & Digital Marketing.

i have a book that might be useful , merkator , but it's in french language :::

You can get access to great industry specific, certified courses on the two following websites -

www.coursera.org

www.edx.org

you can get diplomas, certificates and degress from a lot of leading educational institutes