Because the list is so long, and a bunch of the cons mention cost, I'm going to flog my friend's company, Cloudability (http://cloudability.com). They help you track and control your cloud spending and they're an AWS solutions provider.

There are only three of us at Stayhound (http://stayhound.com), so our list is pretty short:

Mockflow for creating and sharing flows and wireframes

MailChimp

Google docs & calendar

Gmail IM

Google+ hangouts for team video conferencing

Trello for task management

Capsule CMS

Github

Google AppEngine

And we're in the process of considering a move to AWS.