Storing your digital resources "in the cloud" has become a popular way to have access to resources from any computer as well as sharing your materials with others. There are many options with different functionalities and the one that you choose will depend on the equipment you are using as well as the purpose you have in mind.

Google Apps, including Google Drive and Google Docs for documents, forms, spreadsheets, slideshows and more. This is probably the most well-established and the one that I am most familiar with.
Microsoft SkyDrive for documents, slideshows etc. is relatively new and seems to have all the features of the alternative cloud storage options, inlcuding the ability to upload slideshows while preserving the animations.
Apple iCloud for music, mail, photos, calendars, contacts, notes, documents etc. works well for iPad and Mac users.

Evernote and Dropbox are applications you can install on computers and iPads that allow you to share files (including documents, photos and videos) between users and devices.