Dropbox is an easy to use freemium cloud storage solution. It has a client sync utility for multiple platforms.

Box is an online file sharing and content management service.

Koofr offers safe EU based cloud storage with 2 GB free cloud storage space for life and options to connect multiple cloud accounts.

Agora is a platform for generating actionable insights on social messages.

Google drive is Google's cloud storage solution for storing files in the cloud.

Copy.com is a discontinued cloud storage service that offered near-unlimited space and huge bonuses for referrals.

Pogoplug is cloud storage for your mobile life. Access all your files, photos, music and movies wherever you are.