The Internet Archive

Nonprofit organisation established to preserve Web sites by taking regular "snapshots".
http://www.archive.org

Ghost Sites

Long running online "museum" provides screenshots of defunct sites.
http://www.disobey.com/ghostsites/index.shtml

Textfiles

Contains information gathered from BBS's in the early days of the Internet.
http://www.textfiles.com/

NoveltyNet

A site where people can submit orphaned content to be archived and kept available.
http://www.noveltynet.org/

DevArchives

Contains archives of FAQs, mailing lists, and newsgroups all related to developer/programming/IT. Free.
http://www.devarchives.com

The Register: Archive.org Suffers Fahrenheit 911 Memory Loss

Opinion piece by Ashlee Vance about how archive.org doesn't permanently save material the way most people believe it does.
http://www.theregister.co.uk/2004/07/09/archive_yeahright_org/

The Register: Britain's Web Presence to be Saved

Announcement of the creation of the UK Web Archiving Consortium (UKWAC).
http://www.theregister.co.uk/2004/06/24/web_archive_british/

The Register: The Web as Historical Record

Essay by Peter Abrahams pointing out "one of the weaknesses of most search engines and the Web itself: you cannot sort by date."
http://www.theregister.co.uk/2004/05/04/web_historical_record/

The Register: Google, the Only Archive We'll Ever Need?

Opinion piece by Andrew Orlowski. Points out that Google can't always index, retrieve and/or sort everything in useful ways, but its supporters are overlooking these major drawbacks to using it as an archive.
http://www.theregister.co.uk/2003/09/15/google_the_only_archive_well/

First Monday: Internet Time and the Reliability of Search Engines

Journal article by Paul Wouters, Iina Hellsten, and Loet Leydesdorff. Examines the consequences and implications of internet search engines continuously reconstructing the past by updating their indices.
http://www.firstmonday.org/issues/issue9_10/wouters/

Searchenginewatch.com - It's Tough to Get a Good Date with a Search Engine

Article by Gary Price and Genie Tyburski. Explores the question of "what is a date on the web?" and notes that a searcher may be misled by the results of searches restricted by date.
http://searchenginewatch.com/searchday/article.php/2160061

Google Groups

Searchable archive of more than 700 million Usenet postings from a period of more than 20 years.
http://groups-beta.google.com/