Facebook, Twitter, LinkedIn
From May 2013 - Feb 2015, I was able to grow Spartan Tool's Facebook page by 128% and create an engaged following of customers almost entirely by organic methods (with a max boosting budget of $50/month). Through the implementation of several successful post series (particularly #spartanatwork posts, which showed customers using company products), the page grew website traffic and became a key source of customer recommendations and reviews, as well as a community to discuss techniques and best practices.
While social media has not been as big of a priority to WBA leadership (especially in light of the increasing pay--to-play market), the WBA maintains a regular presence on Facebook, Twitter, and LinkedIn, and uses small boosts to promote particular news and events.
Particularly for an association, regular email communications have been crucial for sharing relevant news, strengthening our reputation as a thought leader in the housing industry, and increasing retention. The WBA's 4,000 members typically receive 2-3 communications per week, including regular series such as the biweekly "Blueprint" (an advocacy news piece) and a quarterly e-newsletter. The WBA also reaches out to new members monthly, and--internally--shares a monthly digest with local association staff. WBA open and click-through rates trend from a few to several percentage points higher than the industry average for associations.
During my time at Spartan Tool, email campaigns enjoyed an average open rate that was 3% higher than industry average, and a click-through rate that was 5% higher.
I have primarily used Constant Contact for email marketing, but I am also familiar with MailChimp.