As most people can't sort out Ventrilo for fleet speak, can I suggest the alternative of Skype?
Skype's not a bad suggestion, but not everyone has a camera, so most people will just be using the voice, at which point I don't think it's much more useful than Vent.
If you need help getting Vent set up, I can do that.
The biggest problem with Skype is when you only have four or five people it's fine, but when you start adding more people and get over ten it gets super laggy, because there's no such thing as dedicated Skype servers.
On the other hand, I HAVE a dedicated Vent server...