blockdiag [0] has several helpful types of text to diagram processors with several output filetypes like svg and png.
In particular I like nwdiag (network diagrams), rackdiag (server rack layout) and packetdiag the most.
There is also an interactive web form [1] to try it out. You can switch between the types of diagram in the top right dropdown.
I second blockdiag and it's variants. One of my half done side projects is an automatic network scanner and mapper that is versions so you can walk back in time on the network with netdiag. The only downside to me is the non gpl license.
There is also an interactive web form [1] to try it out. You can switch between the types of diagram in the top right dropdown.
[0] http://blockdiag.com/en/
[1] http://interactive.blockdiag.com/nwdiag/