GitHub - Code repositories
Springloops - Deployment
Pivotal Tracker - Agile planning tool
Podio - Get work done
New Relic - Server/Application performance monitoring
Pingdom - Uptime monitoring
Blame Stella - Speed monitoring
Sendgrid - Email delivery
CloudFront - CDN
Free services:
Groove - Support tickets & chat (groovehq.com)
Trello - Organization
Stripe - Payments