Discussion: What Premium Apps Do You Use?

It seems like everyday there are more and more paid applications coming out to make our life easier. Pioneers like Freshbooks and Basecamp have set the bar for such applications. But with so many great (and not so great) alternatives to these, how do you know which premium apps are worth paying for and which aren’t? Sure you could test all the free ones, but who wants to do that?

Anyways, my question this week is…

What premium applications and services do you pay for to run your business and why?