No secrets here... in fact, I think a lot of this is in the kbase already.
We run Debian Linux 2.2 (potato) on all of the web machines. Some of the mail servers and back-end machines are running the next release - 3.0, aka 'woody'. We're currently using version 2.2.19 of the Linux kernel on the web machines (again, with some of the backend machines running later versions). All of the machines are i386 type machines.
As far as what packages we have installed, we don't restrict access to this information; if you know how to use the debian package tools (dpkg), you can view what packages we have installed.
dpkg -l | grep ssh
dpkg --get-selections | grep ssh
Debian is a bit of a pain to install at times, but it's very easy to maintain, and we generally use the vendor supplied packages for most stuff, although the apache and php packages (as well as some others) have some customizations.
If you want the machine to have the same versions of stuff as our machines, I'd suggest using Potato; Woody is a lot more usable, though - it has much more up-to-date packages. Personally, I like the BSDs (mostly FreeBSD) more than Linux in a lot of ways, and that's what I run on my machines... but if you want something DH-like, Debian is the way to go.
More info at: