well im about to launch a support company, and i couldnt reccomend anything else other than
http://www.omnistarlive.com/ it has everything i need, but this is tailored for what i am doing
perl desk looks pretty good though i have never used it.. no live chat though which effected my decision
if you have hosting with cpanel it offers a lot of scripts for free through fantastico
Crafty Syntax Live Help
Help Center Live
osTicket
PHP Support Tickets
Support Logic Helpdesk
Support Services Manager
didnt like many of these but osTicket seems pretty reasonable (because it is free!)
trial and error is the best way to get aroudn these, all of them promise awesome functionality etc... but some are really damn annoying to get going.
good luck, it took me ages!