If you decide to build a house, would you start by asking, "What are the best construction tools?" Probably not.<p>Start by defining what it is you're trying to do. Are you trying to get more visitors to sign up for a trial? Are you trying to lower the bounce rate on your homepage? Are you trying to get more lifetime value from your existing SaaS users? ...<p>A list of tools won't help if you don't know (or don't specify) what you want to do.
Not open source but Colibri is pretty nice. <a href="http://colibri.io" rel="nofollow">http://colibri.io</a>.<p>Also check out <a href="http://iwantgrowth.net" rel="nofollow">http://iwantgrowth.net</a> for potential websites where you can find more resources.
For startups, we have a handful of growth hacking resources here:<a href="https://globality.be/tools?tags=Growth+Hacking" rel="nofollow">https://globality.be/tools?tags=Growth+Hacking</a>