Ticketing system... what are you using?

Ok, this is targeted to those that have many money sites and also using a 'support' site. Or those that provide a support service for other sites and from your own.

I'm looking for a ticketing system, that users from my 'money' site support questions (contact us form with different categories) are funneled to my support site, but when I reply to them, it's as if sent from the money site. I'm getting tired of supporting each site indepenantly and wanted to have a centralized location. My support site is joomla based, so would be nice to have something I can integrated into somehow.

I'm just in the planning stage so open to any and all suggestions.