Google Drive is the most reliable and free cloud drive available in the market. It provides 5GB of space (you can purchase further disk space) and lets you sync your files on Desktops, Android, iPad, iPhone and through browser on unix/linux based platforms. You can also use Google Drive to backup your critical files on the cloud and access those files from any Android phone/ iPad/ iPhone or through browser.
You can download Google Drive from here.
Desktop Download: https://tools.google.com/dlpage/drive/?hl=en#eula
iPad Download: http://itunes.apple.com/us/app/google-drive/id507874739?mt=8
Once you have installed Google Drive, you will see following thanks popup box.
Next screen will ask you to Sign-in with your google account
Type your user name and password, click on “Stay signed in” if you are the only person using this desktop/laptop.
Now click on “Advanced Setup”
Select the folder you want to sync online. First time you need to create an empty folder and sync your existing online files. Afterwards you can save your documents and files in the folder.
You are almost done. Now you can now download Google Drive app in your android or iPad also. You can also access your online drive from your browser at URL : http://drive.google.com .