Next to the paid software, I don't really think there is anything good. The other free help center suites are, if I remember correctly, quite out of date. As in the last update on a few of them was 2k4. Not that HCL is doing much better, but it is a bit more up to date. If you want to go paid software, there are quite a few decent ones, and I would be happy to help you find something. However if you want something free, you may be best building a basic system yourself. I made one that allowed operators to use MSN in about 15 hours. Its not extremely featureful, however it works on windows and macs

Spenser