A full export of each wiki is created once per day. The export includes all pages, history, discussion pages, files, images, and categories. It does not contain any user data, such as passwords, password hashes, emails, or cookies, although it does contain a record of which user names created which revisions for each page.
This is a MediaWiki XML dump, so it can be used to run a functioning copy of the site. It can probably be converted into other formats as well.
Most importantly, these copies are stored at archive.org. Daily backups are stored on archive.org for 30 days. In addition, monthly backups, taken the first of each month, are stored on archive.org indefinitely.
You can download the backups from archive.org here:
Here is a direct link to the archive.org downloads:
In addition, you can also download these backups locally:
You are encouraged to mirror these backups yourself, since the more people have it, the more the information can live on.
You can also download a backup of the old Wikispaces wiki here on archive.org.