Ohh I bet I know what it is. The community is probably f-locked, so only members can see posts.
If you have an LJ account it might be worth joining! It was incredibly active during series 3, and there are a number of jaw-dropping fics. (Mine are actually the worst of them, haha.) I don't think membership is moderated, all you should have to do is hit Join Community and enjoy.
It's the-thickofit.livejournal.com
There are several variant comms floating around with hyphens in different places, but that one is the comm with (afaik) all the fics.
The internet always, always needs more Malc/Jamie.