I'm a big fan of what @destraynor and team at Intercom have built (we use it on Product Hunt). Segmented and one-on-one user messaging is incredibly powerful when used correctly.

I spend more time on Intercom than any other tool. Including email.

I use Intercom daily. Fantastic product and great customer support.

It's the CRM for growth hackers with the ability to track and execute life cycle campaigns with the greatest of ease.

Blown away by this product.

Not only is the product great, so is their blog series.

We use intercom at Process Street and love it! We are not even using it to its full potential yet but have big plans :D - plus the guys are always rolling out new features to make the product even better, especially if you are a single page JS app