I asume there is still mutliplayer somewhere.
It's a bit more involved to set up than just clicking a button and the game taking care of the rest (though it
will do this
after you set it up the first time), but it's there

First, go to
This Multiplayer FAQ on the
Game Warden Forums. It is a detailed walkthrough of how to set up multiplayer on FSO. Since you already have the game, skip step 2. With that out of the way, go to
This Thread here on HLP to pick up the multiplayer mission package, which I recommend putting in your mediavps directory if you want to play with those that enabled, else in a seperate mod directory. Either way, never stick a 3rd party VP (even one as official as this) in the freespace root directory. Note, you may not need to DL these if you used Turey's installer to get the game. And that's it, you're done.
And now, as promised, all you have to do to enter the multiplayer game lobby is to start the game, pick your MP pilot, and click on the ready room. That doesn't mean there will actually be any games happening, but that's a different matter - And you can always make arrangements in advance to have people show up at a designated time.