Dia is to create all kind of diagrams: UML, company relation, flow charts, network diagrams, electric diagrams and much more.
Dia is easy to use and you can save the drawn diagrams in EPS, SVG, XFIG, WMF and PNG and XML format.
Dia has similar functions to the Microsoft Vision program; the only difference between these two programs is that the Dia is free.
Due to this program is so easy to draw diagrams that you just need to drag and free the figures we want to draw to join them in lines. Moreover you can print all the diagrams with no problem at all.