According to http://en.wikipedia.org/wiki/Scala_%28program%29 :
"Scala ... allows users to create ... musical scales..., play them with an on-screen keyboard or from an external MIDI keyboard ... retune MIDI streams and files using pitch bend ... supports MIDI sysex and file-based tunings ... export them to hardware and software synthesizers ... as a midi sequencer, ... its ASCII-based sequencing format ... is ... very powerful ... its use of human-readable text files to store musical scales ... has become a standard for representing microtonal scales ... The Scala site lists over thirty applications that support the format, including several major commercial packages..."
Installation and configuration of Scala can be a bit tricky but if you follow http://www.huygens-fokker.org/scala/downloads.html carefully, it should be relatively painless (remember to get the "Scale Archive" near the bottom of the download page too).
"For trying out 19-TET", after starting Scala, type the following command into where it tell you to "Type any command below here" near the bottom (and hit the enter key):
EQ 19 2
Then, click the play button (i.e. on the row of buttons named [Open] [Save] [Input] [Edit] [Stop] [Show] [Comp] [Play] [Relay] [Send] [Freq] [Opts] near the top, and play with the on screen musical keyboard that pops up using your mouse. After having fun with that, you may want to issue the following command to Scala for it to tell you more about how to use it: