Few years ago, Joshua Schachter started this thread on HN for discussing hosted useful services: https://news.ycombinator.com/item?id=1769910
The contribution in thread introduced many interesting SaaS services which can immensely help in deploying services as well as development.
It's been three years since then. What do we have today?
1. BitBucket (http://www.bitbucket.org) - Source code hosting
2. Google Docs (http://drive.google.com) - Team Collaboration
3. BitBucket Issues (http://www.bitbucket.org) - Team Collaboration
4. Heroku (http://www.heroku.com) - PaaS/sysadmin replacement
5. Hirefire (http://www.hirefireapp.com) - Scale up/down dynos on Heroku based on traffic
6. Mongolab (http://www.mongolab.com) - Database-aaS
7. Pusher (http://www.pusherapp.com) - WebSockets-aaS
8. Filepicker (http://www.filepicker.io) - Uploading files to the application
9. Mailgun (http://www.mailgun.com) - Send & Receive Mails
10. PaperTrail (http://www.papertrail.com) - Error Logging (Rails)
11. Errorception (http://www.errorception.com) - Error Logging (JS)
12. Desk.com (Knowledge Base + Customer Support)