First off, make sure you sign up for the PR Forums.
Read this post:
http://www.realitymod.com/forum/f137-pr-game-tactics-strategies/27725-common-mistakes-project-reality-apheirox.html
Use [PiCE] tags when you are ready to move from Co-Op to deployment and AREN'T going to be a griefing Dbag.
PiCE Server (Currently offline) Is PiCE Urgent Insurgency. Name may change, we'll see what people want.
Ventrilo and Full-install (i.e. not the one that comes with PR) are both at www.80hd.net
The private PiCE Channels in Mumble are passworded with "iceman" (Will confirm this is the right case)
Make SURE you connect to PR Mumble for 3D positional awesomeness! Even if no one else is in that servers Mumble, I have seen up to 10 people join after I logged in when it was empty. PR Mumble address is mumble.realitymod.com