We use Hey Bubble for our website and this is neat. Easy to use, easy to setup, very nice customer service. Great product
This service should be much higher on the list. They provide great info on your customers, and work really well with Adium on the Mac. Top notch customer service as well.
In terms of backoffice support - the best choice available.
Without any doubt the only service that manages to both have advanced features and user friendly interface.
I like when it's free!