New Relic is a priceless tool that allows you to monitor the health of your app and immediately uncover any critical issues.
Making decisions based on data and learning from them has become one of the most critical competencies of successful startups companies. Optimizely makes it incredibly easy to start A/B testing various elements of your website and thus accelerate your startup learning.
Mixpanel is quite powerful in terms of what it can track, and they have very good pricing--you can use it for free in the beginning. We're not super excited about it, though--we wish we could better send emails and do more proactive things with it.
We love Close.io. It has an amazing UX, which allows you to cut down on data entry and focus on closing more deals. I can’t stress how much it has simplified our sales and account management processes.
LiveAgent is a great tool--it handles everything. Nothing is more important in the early stage of a startup than making your first customers happy. LiveAgent seamlessly combines email support, knowledge base and powerful live chat, allowing you to focus on actually helping your early users. The setup could be a bit easier, but it offers priceless gems such as automation rules, ticket reminders or proactive chat for a great price.
We use MailChimp for newsletters. Email marketing is not a big part of our strategy at the moment, but it will become more so, so then we'll probably take a better look at the tools.
InHiro makes it very easy to create customized pages with information for hiring. We can manage our whole recruiting pipeline with them--from promoting our jobs over social networks to keeping track of where a candidate is in the hiring process.
Trello is fantastic, and we use it for almost everything. It's an easy-to-use kanban board tool that allows you to effectively organize your projects, ideas or even daily to-do lists across all of your devices. This is probably the tool I rely on the most during my day. It's also incredibly flexible and requires no setup or training.
We had also been using Trello for product development, though we just recently added JIRA for our engineers. More substantive and has more integration capabilities than Trello, though Trello is much easier for early-stage startups. With JIRA, there's some upfront work that needs to happen before you can use it effectively--you need to know what you're doing and what you want from the tool to set up JIRA well.