Creating flowcharts, diagrams, and other data visualizations often means making an investment of nearly $600 in a copy of Microsoft Visio, for what can ultimately turn out to be relatively simple design work.
Lucidchart covers all the diagramming basics for free, and for just a few bucks a month you can access extra features such as mind maps, mobile app wireframing tools, and version history (as well as additional users and more storage space). You can collaborate with other users on complex charts, and share the finished product on Facebook, Twitter, or Google+.
Lucidchart comes in online and desktop versions. The latter works offline as well.