We have a 'hooks' module for smileys installed in Postnuke (it's there for the shoutbox on the front page)
I've enabled smileys for news items so if anyone considers submitting a story and they fancy the odd smiley in there, just use the standard code, e.g.
:-) :-P :-D :-o :-( etc..
I've no idea as to how many smileys i'll know about, but all the common ones will be in there (needs the '-' in it though..)