Hawknet Computing now runs a Mumble server. This Mumble server is very similar to Teamspeak, however offers more administration, and is lighter on memory.
You can download the client here!To connect to Hawknet Mumble, after running the program, go to "Server" and then "Connect" or press 'CTRL+O'. In the new window, bottom right, hit the 'Add New...' button, and fill in the information in the new popup window.
Login information is: hawknetcomputing.co.uk with a port of 9987
Create the username you desire when logging in. If you register your username (for any sort of rank) you will not be able to change it, so make sure it's one that sticks.