free/open documentation formats

[Timo Boewing <blazko@online.de>]

Hello all,

for some future and current works i want to provide my writings 
additionally in other formats than xhtml. Has anyone a link to a list 
of free documentation formats? The problem is that i want to avoid 
using formats on that evtl. patents are pending.
for example, i would like to provide my stuff using portable document 
format (pdf) and postscript (ps), but i am not shure if the formats as 
such are free cos adobe has a trademark on them.

any hints?

thanks in advance,

Timo

p.s. i would be happy to get some hints on good viewers. should be 
pure console/X/gtk viewers. e.g., is there a substitute for acrobat 
reader that does also do well?