We use a vast array of online tools and services at Snapt, many of which took us quite a long time to find and/or choose. At a startup I believe it's important to leverage the best services to accelerate what you are trying to do: don't build a datacenter, use a cloud.
This isn't a list of all the products we use, but rather some of my favorite lesser known products we use at Snapt.
As a software company you can imagine the number of programs, tools and services we use. However, there are some standout favorites of mine.
CircleCI - continuous integration and delivery. Easy to get into and get set up at a low cost.
Code Climate - automated code review for test coverage, complexity, duplication, security, style, etc. This is my favorite auto-code review service.
Opteo - automated AdWords optimization tool. I love Opteo, it really will save you money and improve your conversion rate.
Segment - Over 200 Sources and Destinations empower your team to use their favorite tools to personalize campaigns, analyze product usage, etc. An awesome way to manage all the various online services you use on your website and shop.
DigitalOcean - DO is actually rock solid. We host in AWS and DO and have very little downtime on either. DO is great for spinning up test environments, demo servers, etc.
Termius - I love this SSH client so much. It has SFTP included, and profile sync (with keys) between my Mac and Desktop.
Pingdom Speed Test - a great waterfall based website speed test.
SSL Server Test - monitor and check the security of your SSL web site.
1Password - I prefer this slightly over LastPass. They both have team support though and are a much better solution than remembering and having shared passwords.