Hmm, well, people have pimped Solaris and Debian, so just to confuse you, here's pimping FreeBSD. (Even though I use Solaris and RH Linux in production, but anyway).

My most important production servers run FreeBSD. I've had FreeBSD boxes running naked out in wild for years with not one single comprise. The main reason, I guess, is that the kernel and userland live together and it's relatively easy to bring the whole mess up to date. Gentoo's emerge is the closest (and I'll freely admit, in some ways better) that Linux gets. FreeBSD ports can be sucky at times, but basically work. Apache and mod_perl you'll want to compile yourself anyway, so that's not so much of an issue.

I've had lots of grief in the past with g?libc upgrades in Linux, for one reason or another. I've had even more grief with Solaris patches getting lost in dependency hell between 32-bit and 64-bit versions. Touch wood, I've never had any of that sort of trouble with FreeBSD.

I don't see any reason to using Red Hat specifically. If you're going to go proprietary, go Sun. If you're going to go libre, go Debian.

The most important issue is to make sure you have decent hardware with a good slab of RAM and SCSI or Serial-ATA drives in a hardware RAID configuration. Any modern operating system will serve you well on good hardware. They all have their warts; go with what you are comfortable with.

Don't recycle old Celeron desktop boxes. That way lies pain and madness (been there, done that).