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.

[0] http://blockdiag.com/en/

[1] http://interactive.blockdiag.com/nwdiag/