Google Talk allows text and audio communications.
The only problem is that service is only yet available on Windows.
It is thus possible to use iChat, but for text only, thanks to the Jabber protocol.
Please note that you'll need a GMail account to get access to the service.
[Update]bad_duck, a member of our team, told us that audio conversations are working with iChat, in contradiction with what Google claims.
[Update2]After further investigation, bad_duck informed us that it is not yet the Blue Sky he announced.
In fact, it does work like this only if you are using 2 iChat clients: there is a sort of recognition in the software that allows then audio (and even video) - status are also regnonised but not file transfer or avatars. Between iChat and the Google Talk client, the chat is text-only.
It is not then the announced alternative to Skype to make audio conversations between MAC and PC :(
Another issue is that the jabber server from Google is not connected to other services so you'll have to choose if you want to use Jabber in iChat for Google or the other services, such as MSN or Yahoo.
