For your documents, Dropbox is an online storage system that can make sharing easier. Available for Windows, iOS, Linux and Mobile, you’re able to sync up all of your files with each of your device. Why run to the office when you can access all of your last-minute files from home? Best of all, a 2GB Dropbox account is free!
I use ifttt.com (a really cool web site I found) to backup pictures from Facebook that I am tagged in to dropbox. There are LOTS more uses, but for backing up files and sharing this is one site that can be used. It creates a folder on each of your devices and puts a backup on each device.
An other of my favorites is Google Docs – You get a large amount of space for free, but you can also pay $5 for the year for a larger account. You can invite your friends to share and edits are even tracked. So far I haven’t had a problem with concurrent edits.
Skydrive is Microsoft’s equivalent to Google docs. I use it for files that are Microsoft derivatives – like Excel Spreadsheets. If you are already using Microsoft for the files it’s easier to just stick with the same file type.