Google Drive is Google's file sync app that lets you store all of your files online alongside your Google Docs documents, and keep them synced with all of your devices.

Dropbox lets you store your files online, sync them to all your devices, and share them easily. Get started for free, then upgrade for more space and security features.

OneDrive, Microsoft's file sync app formerly known as SkyDrive, lets you store your files online, edit Office documents in the free Office Web Apps, and easily access your online files from your PC.

Box lets you keep all your businesses files in one place for simple online collaboration.

Amazon Simple Storage Service is a fully redundant data storage system. It makes it easy to store and retrieve any amount of data, anytime, from anywhere.

CloudConvert converts files between more than 200 supported formats: documents, image, spreadsheet, presentation, audio, video and more!

Citrix ShareFile is an enterprise "follow-me" data solution that makes it easy for users to store, sync and share data securely from any device, anywhere!

Egnyte enables users to easily and securely share files on-premises and in the cloud. Egnyte’s award-winning platform integrates with any cloud, storage, device and business application to enable customers to optimize their collaboration environments through secure access, centralized control and unified visibility.

Get your own server to send and receive files to and from your clients, vendors and co-workers. Supports any browser, operating system, or FTP program. Flexible permissions and military-strength encryption protect your files.

ConvertAPI is a file conversion service which supports many file conversions from numerous sources and file manipulations such as merging, encrypting, splitting, repairing, and decrypting PDFs.