This isn't a new app, but I've only just stumbled across it. Welcome to Gliffy, a web application that allows you to create diagrams of different types and shared them amongst other people:

http://www.gliffy.com/

This is one of the nicest, smoothest web apps I've come across in a while. Unlike so many other web apps this is incredibly responsive, easy to use and looks great.

The free version gives you everything you need to trial it out, then it's as little as $5 per month for a single user. If you're looking for an easy way of creating network, flow chart, UML or even floorplan diagrams, definitely head over and check it out.