Fantastic use friendly site for creating mind maps of images / information online. Works almost in fairly similar way to prezi. Very easy to learn. Free sign up. Collaborate on mind maps with other people. You can select to be emailed daily, weekly or monthly changes to the popplet. Think you only have 5 free 'popplets' though :(
Cacoo is a user friendly online drawing tool that allows you to create a variety of diagrams such as site maps, wire frames, UML and network charts.
Cacoo can be used free of charge.