I have a lot of success with linked for selling to property management companies. I don't use facebook that much. Twitter is great for conferences etc...
As for property to residents....I'll leave that to the experts.
I think all of them can be used successfully for specific reasons. Facebook for engagement and keeping in touch with residents, partners, etc., Twitter to share articles, Linkedin to network within the industry, and Pinterest just because people just love visuals. Choosing the right social platform really all depends on your purpose and what you want to do with your business.
That's a question I've been trying to figure out for years. I wish there was a network for maintenance techs to discuss various equipment and repairs but have not found one.
@David I love MailChimp as well. I think most property managers/marketing directors know enough to create their own email campaigns. Once a month would be sufficient in my opinion. If the property managers/marketing directors can see results from an email campaign, I believe they would continue use them. I feel that email campaigns have been under utilized specifically in this industry and now with services like MailChimp it is a lot easier to make professional emailers than it has been in the past.
Do you think most property managers - or Marketing Directors, for that matter - know enough about email marketing to create their own campaigns (MailChimp, Constant Contact, or custom HTML as Jeff mentioned)? My gut says, sure, but I think they'd likely stop after the first one or two.