jive software
if you have a java server running, you can check out openfire/fastpath/spark combo at igniterealtime.org
we have been using it as a replacement for liveperson for almost a year
i don't think it has been updated for some time, but it works relatively well
i've been trying to get osticket + the spark client integrated for ticket lookup and such, but that is probably not going to happen at this point in time.
