Multi-party key agreement I have done a google search for "multi-party key agreement", and there doesn't seem to be anything more recent than about 2005.

Are there any practical multi-party key agreement protocols known?  

To be more precise, I want a protocol which:


Allows multiple individuals to agree a single shared secret
An adversary cannot tell what the shared secret is by listening to the communications.
It should be authenticated so an active adversary cannot persuade a participant to communicate with a secret the adversary knows.


Note: I am aware of Multi-party Key Exchange protocol from lattice but a) that doesn't have any answers; b) I am not only interested in lattice cryptography (in fact, I would prefer something based on ECC or factoring).

Edit: Background
I want a system for encrypting a conference call.  If each caller sends their audio to every other participant with separately agreed keys, then the total amount of work required is $O(n^2)$ (and the work done by each participant is $O(n)$).  If everyone agrees a single shared secret, then we might be able to reduce the amount of work required.
Historically, both the difficulty and the risks involved in securely establishing shared keys in large networks has led to the invention of public-key cryptography. So you might first want to consider using digital signatures/asymmetric encryption instead of sharing the same secret between parties. 

If you need all (or some) of the parties to collectively sign or encrypt a message, consider using threshold signature schemes with a Distributed Key Generation protocol. That will produce a key pair that is distributed among $N$ participants such that at least $k$ of them need to collaborate for performing a key operation. For discrete-log cryptosystems there's a paper by Gennaro et al that describes such a setup.

Edit: If you only need to establish a common secret (instead of a key pair) between all the parties, a simpler solution would be to use a generalized Diffie-Hellman key exchange instead. This works for honest participants with insecure communication channels. If the participants can be malicious, a more robust solution is described by Tseng, 2005.