Ask HN: How do you support your users/clients?

Hi all. I'm looking for a great way to handle support requests from our clients. We're a 6-man consulting shop, but we also provide ancillary services to our clients such as web hosting, network administration, etc. Our current support system (which isn't really a 'system') is very inefficient. We are thinking of providing 1 email address which is delivered to some ticketing system (advice on software is much appreciated) and 1 phone number for absolute emergencies (I realize the impact of this, but our clients expect this level of support). Our first thought was to roll our own ticket tracking app, but then we calmed down and decided to survey the landscape a bit before coding it ourselves. Most of the open-source projects I've found so far seem antiquated or abandoned. Does anybody have a system that they absolutely love? Much Thanks!