Right now, a group of our employees is using Skype for group chats and conference calls. They're not using telephone numbers, just Skype user accounts.
I'd like to set up a server that will provide similar functionality that is only accessible inside the LAN.
What I'm not looking for is something to use with real telephones.
The main problem with Skype is that the Linux client is terrible and getting worse every year they don't update it. I also don't like the idea of our company data going through Skype servers (yes, I know it's encrypted).
SIP seems to be quite a pain, but there's also GnuGk and Jabber+Jingle.
Whatever it is, I'd like to also support Windows clients.
Is there anything out there that's open source and easy to administer?
openfire (server) spark (client)
both are released under the gpl
You should take a look at Unison (www.unison.com) -- Linux on the server side and Windows/Linux on the desktop.
Although originally stemming from the computer gaming scene, TeamSpeak has become a fairly usable cross-platform VoIP client.
The only problem would be that TeamSpeak in itself does not really offer messaging capabilities. And, as I just found out while checking up again, they are actually charging license fees right now for commercial server usage.
SIP is the most commonly supported protocol for voice over IP. Building a local Asterisk server sounds like the easiest thing to do. Something like trixbox, Switchvox (free edition), or even Digium's AsteriskNOW will get you exactly what you need. All of them come with conference ability and all support the SIP protocol so any SIP soft phone will be compatible.
Could you not set up separate Voice and Messaging (Asterisk / [Jabber|IRC], for example) and integrate authentication? A Skype replacement might not be available.
I'm kind of surprised Asterisk doesn't have a plugin or extension for text chat. At my workpalce, Cisco / Avaya / Office communicator are heavily integrated for voice/email/chat/conference.