UPDATE (July 1): MobileMe is officially closed, but Apple is for a "limited time" offering links for users to access the services and retrieve their files, as well as upgrade their existing accounts to iCloud.
Tomorrow, Apple will be closing down its MobileMe online service in place of its new iCloud offerings. While some of the previous MobileMe services have been continued in iCloud, a few of them including Web hosting, photo gallery, and the iDisk online storage option will be shuttered. If you have used MobileMe for various hosting or storage purposes, then be sure to log in to MobileMe and back up your data because after tomorrow you will no longer be able to access your files.
Apple has been regularly reminding users of this impending closure since the new iCloud services were announced, and has sent out e-mails instructing users to download their files from MobileMe. To aid in this process, Apple has added a couple of file download options to the Web interfaces of its MobileMe services, which you can use to quickly get all of your files.
We previously covered how to log in and quickly download your files from MobileMe, so if you have any Web sites, photos, or other files you have stored on the service then be sure to check out this blog post on how to access and download your files. In essence, after logging in you just need to go to the gallery and click the download button at the top of the page to get all of your photos and albums, and then go to the iDisk section, select all of your folders (press the Shift or Command keys while clicking to select them all), and click the download button to have the service zip up your files and download them.
While Apple is encouraging users to download files from its services that are closing, not all of the MobileMe services will be shuttered. The calendar, e-mail, contacts, and bookmarks syncing options Apple has supported will remain as part of iCloud, so once you have logged in to your MobileMe account and upgraded it to iCloud, then these services should continue working. Upgrading to iCloud can be done either through the iCloud Web site or through the MobileMe system preferences in OS X.