People change, computers change, however, the way Internet musicians exchange tablatures hasn't evolved for years. ASCII text, is still the only way, just because it is still the most practical. 
Tablature offers easy authoring, graphic rendering and playback ! ... and is a freeware
For the author, Tablature Editor allows easy edition and publication of Guitar and Bass tablatures.
For the Web surfer, the Tablature reader, which is a Java applet, is automatically downloaded when needed.
The goal is to promote an open standard (XML based) to describe tablatures, and eventually associate this concept to other music exchange networks like Napster or Gnutella.
Here are some cool samples of tablatures
After installation, read the user guide.