I'm pretty sure (or at least I hope) that since you all know about The Core, you've heard of the other Black Mesa oriented modification, Half-Life: Particle Fusion. I'm in dire need of some people who are willing to help me out in the mapping department. I've already got all the other bases covered (programming and modelling) so all I need is another guy to help me out.
If you're interested you can see some of the stuff I've already done here.