Google sent emails to Google Groups owners notifying that they'll be phasing out Groups. So, "starting Jan '2011 you'll no longer be able to create or edit customized welcome messages, pages or files. Such content already on your groups will become read-only. By February, these features will be turned off altogether."
Google allows you to export all this content into a ZIP archive -- by going to your pages or your files homepage on your groups and clicking Download all pages or Download all files.
As for alternatives, Google recommend using Google Sites for page creation and Google Docs for file storage. Pages made in Google Sites and files uploaded to Docs can be shared with members of groups. While these solutions probably require a bit more work than the features available in Groups, and mayn't integrate as well with Groups.