Google Drive, SkyDrive (soon to be known as OneDrive), Dropbox, and SugarSync offer users varying amounts of storage for varying prices. For each, prices start with a free account.
Of great interest to iPhone users should be an offer from Box.com. The company is offering 50GB of free storage forever for iPhone and iPad users. This offer runs through February 15. Those who already have a Box account are also eligible to expand their free storage to the 50GB.