One thing that makes MailChimp unique is its open API, and the number of 3rd party
integrations that have resulted from that (check them all out here).
Here are some recent integrations:
1. Hootsuite (share campaigns to any of your social networks, view campaign results,
and more... all from within your HootSuite account)
2. Pinterest (send automatic e-mail campaigns with content from your pin boards)
3. Instagram (send automatic e-mail updates from your company's Instagram feed)
4. and, finally, Zendesk (deeper integration between MailChimp and everyone's favorite support tool)