The FAQ mentions that you can download portage-snapshots from http://cvs.gentoo.org/snapshots. However, this link doesn't work (anymore). Reproducible: Always Steps to Reproduce:
this is right snapshots are on every GENTOO_MIRRORS avaiable the next thing is, that i don't like the whole "What if rsync doesn't work for me? " when you download the snapshot every day and unpack it, there are phenomical things emerge does. there are 2 ways out: 1) add that the directory should be removed every time (Attn, the distfile is too in there -> make.conf distfile overlay) or 2) portage 2.0.47+ contains emerge-webrsync, which fetches the snapshot, unpack it and rsync the portage tree with the snapshot when asking me, i prefer the 2. option more !!!
The snapshots are really in www.ibiblio.org/gentoo/snapshots (ofcourse, they are mostly also in the mirrors).
Updated URL for portage snapshots to http://distro.ibiblio.org/pub/linux/distributions/gentoo/snapshots/