Is there a way to setup an extension in the extension.conf to block the “user” from using outgoing calls? In other words allow them to call other extensions on the network/server but not use the VOIP or analog adapters?
Yes. Read about contexts.
We use it to make sure one can’t call “pay-lines” (well, 0900 in Belgium that is 
)
[custom-paylines]
exten => _90900.,1,Answer
exten => _90900.,2,Playback(pbx-invalid)
exten => _90900.,3,Hangup
This way all calls going outside (9) and starting with 0900 get the invalid tone.
Hi,
I have just been working on it. We needed a more dynamic way than contexts, so we use a macro that queries the underlying database for the rights of the user, using regular expressions. This macro is called every time someone place a call.
If people are interested I’ll see if I can post something in the wiki.
But… Offcourse we are interested… Or at least I am 
Cheers!