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.

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

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.

4Sync is an online syncing tool. Sync & sharing access with cloud storage.

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