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Google Sites, a solid - but for my taste, a bit oversimplified - jab at marrying an online collaboration app with a simple website creator, was initially available only as part of Google Apps for companies and organizations. Now, it's open for everyone.
Google Sites lets you create a simple webpage, and embed documents, photos, videos into it with ease. After you're done with your page, you can invite other users to see or edit the page, with the ability to change access privileges at any time. It's not exactly Basecamp, but it's free and it works well.
As usual, you can check out what Google Sites is about in Google's introductory video below.