You can get it at the central releases server.
If the main download page on the Ubuntu website ever has a problem, or when it no longer has Ubuntu 12.10 (once 13.04 comes out), you will always be able to get 12.10 here:
More generally, if a release's code name is X, its files are available in http://releases.ubuntu.com/X.
End-of-life releases move to http://old-releases.ubuntu.com/X, but the first URL still works as it's made a redirect. URL's to files inside may not redirect. In any case, folks really shouldn't use EoL releases as security vulnerabilities are not patched when discovered.
You can access bootable CD images there. If you did want to use Wubi (which I understand you don't), you could get it there too. For that, you'd scroll down to the bottom.
.torrent files for bittorrent are also there. If you have a reasonably fast Internet connection--DSL or better--then torrents are probably the best and fastest way to get Ubuntu, and it's an easy way to help out by uploading it to others during and after you download it.
You can browse all the supported releases here:
Clicking a release name there goes into that release's folder as explained above.
Weird architecture? No problem!
For the minority of users who want ISO images to install on less common, community-supported architectures, those are on a different server:
Logistics and Troubleshooting
During times of heavy load, downloading from the releases server may be slow. Even during normal load, it's generally recommended to download from a mirror--that usually maximizes speed, makes it so you don't have to wait as long for the download to begin, and provides for the efficient distribution of Ubuntu to many people around the world at the same time.
There's nothing wrong with downloading from the releases server, especially if you have problems downloading using the download page. One of the things the download page does--besides making it easier for novice users to get the right ISO image--is to select a randomized, probably suitable mirror for you to download from.
Therefore, if there's a problem downloading using the download page, it could be:
- a problem with the download page itself, or
- a problem on one or more of the mirrors that get selected.
Either way, the best thing to do (after you've started downloading your file from someplace that's working right, so that's done) is to report the problem by filing a bug on Launchpad against the ubuntu-website-content package. You can search for it, and then report it if nobody else has, here. If someone else has reported the same problem then you can subscribe to the bug to get notifications and show your interest, and (especially recommended, and totally separate from subscribing) you can use the This bug affects link near the top of the bug page to indicate that you are affected.
Before reporting a new bug, or if you have any confusion about bugs and bug reporting, it's a very good idea to read this guide, even though some of the information is not relevant to reporting bugs in ubuntu-website-content. This is also an excellent resource.