Ask NH: What and to who can you outsource part of your system?

As a generalization, outsourcing parts of your system which aren't core to your problem domain makes a lot of sense to me. I'm always interested to learn about a new company thats focused on solving one of my needs. But I'm sure the list of companies (and the problems they solve) that I don't know is longer than the one that I do. So who and what are you outsourcing? I'll start with some basic examples: -Google analytics for analytics -Google ads for ads -Disqus for comments -Postmark for email delivery