In an entry last week (see below), I pointed out how the mail-archive.com site offered a great repository for archiving and providing a search interface for any group's mailing list.
But this Google Group's feature may appeal to some as an alternative. For more, see the Google Group's technote, Can I use Google Groups to archive another mailing list?.
For more on the other alternative I proposed, including a discussion for why either of this is different from proposing that any individual create their own gmail account for reading mailing lists (an entirely different subject/solution), see Need a (safe) searchable archive for your mailing list? Get one for free!.
The mail-archive.com service does have one distinct advantage: it can be setup to hold previous messages sent to the list being archived. Google Groups cannot, for now, so it will only be able to start archiving once you set it up.
Hope this helps someone or some group with a mailing list that lacks its own archive/search/web interface features.