Don't add a new tool unless you're sucking in prospective members from the tool.
Jelly, Pinterest, Instagram, FourSquare, Twitter, Quora, YouTube, Facebook, LinkedIn, Slideshare, blogs are all tools you can use to attract new members.
But how many unique, new, visitors are coming from these tools? I'm betting is not many.
Too often, we launch accounts on new tools because it's a trend. We promote these new accounts to existing members (whom didn't ask for new account). Now the community is divided over two platforms instead of one. That's two platforms to keep updated and pumped with a steady stream of new information with limited benefits.
Worse still, new tools rarely have a big existing audience. They need people like your audience to them.
You have two considerations when creating an organizational account on any of these platforms. Are you sucking new members in or pushing your existing members out?
If you're sucking new members in, that's good. That's a good source of new members. If you're pushing new members out, that's bad*
Instead of creating and managing accounts on new platforms in the vague hope of tapping into a mass, participate in existing groups and communities. Look for relevant forums and groups on meetup.com, LinkedIn groups, Facebook groups, e-mailing lists, and other places that actually have a large, dedicated, audience relevant to your community.
Participate and develop inbound content there instead.
* the exception here is when the tool reminds members about the community and encourages them to visit. Twitter/FB typically fall into this category.