Statsd (https://npmjs.org/package/statsd) + Graphite (http://graphite.wikidot.com/) - monitoring & graphing
Kippt (http://kippt.com) - link and article saving/sharing
Zapier (https://zapier.com/) - like ifttt for business
Heroku's Hosted Postgres (http://postgres.heroku.com) - DB as a service
Also definitely agree with Intercom, Dropbox & New Relic, all great services.