There are quite some web-based visual diagramming tools available, some of which have been featured at infosthetics before, such as bubbl.us, aMap and Life Flow Charts, and some others not previously covered, such as gliffy.com, iplotz.com and flowchart.com (and many others I forgot...).

Lovely Charts [lovelycharts.com] tries to stand out this crowd by making the user-generated flowcharts, sitemaps and wireframes more beautiful than those from its competitors. You can see some of their graphs here, although unfortunately somehow only in a miniscule resolution.

An interview with the creator can be found at Insideria. Via TechCrunch.