Please keep in mind that elementary supports its penultimate releases only slightly into its current release's life. The older software below is unsupported by the developers and is provided here primarily for purposes of history and curiosity.
A librarian once told me about the lifecycle of periodicals. At first, they are common, used, and after some time, they lose their currency and are discarded. Then they become rare and mainly curios for historians. Looks like we're nearing that latter half already.
So the DistroWatch links are down—elementary isn't hosting these anymore—and the major distro archives (the Internet Archive distro collection and http://distro.ibiblio.org) do not carry it. Until they do, the best way to get these will be by torrent. Be sure to check the torrents against their hashes to verify their authenticity by running the command below each section.
Loki 0.4.1 (64-bit)
sha256sum elementaryos-0.4.1-stable.20180214.iso 5c499579e6ba05eed5626abbbb68fc1e3660e23ccb6a27f1a5f7794fed98bd56
- Softpedia also has a mirror of the latest Freya ISOs
- Assorted mirrors: unchecked torrent links, virtual panic, Google Drive, simosnet-livecd, mirror, ac.id
Jupiter (0.1) at the Internet Archive
Remember: Lots of copies keeps stuff safe
I have archived old versions of Elementary OS and I published them online: http://osarchive.sda1.eu/elementary-os
All of the versions are online at: http://osarchive.sda1.eu/elementary-os (as I just noticed the post above already says)