Five free cloud storage options: Backup and share files online

Got files you want to share in the cloud? There are lots of free options.

Online file sharing services aim to make it easy to store, sync and access the files you need, regardless of where you're working and which device you're using. If you want to be able to access a file you created on a PC while you're at the airport with your smartphone, just save it in a folder to be synced, and you'll be able to access it from any of your devices. You can also share files with friends and colleagues, and keep track of changes with version controls.

There are a slew of cloud vendors trying to win over consumers and businesses with their document synching and collaboration services. Thanks to all the competition, the giveaways keep getting better as vendors try to entice new users with more free file space and fewer account restrictions. For instance, SugarSync just upped the capacity of its free file sync plan from 2GB to 5GB, and it removed a device restriction so that its users can now back up and share their files from an unlimited number of devices.

If you're interested in backing up and sharing files in the cloud, here's what you can expect to get for free from five of today's providers:

In addition to 5GB of file space, across an unlimited number of devices, SugarSync's free service lets users upload and sync data from any folder on their computer - not just a single, designated folder. It runs on Windows and Mac devices, and mobile platform support includes iPhone, BlackBerry, Android and Windows Mobile (in beta). It doesn't support Linux, however. Paid plans start at $4.99/month for 30GB of storage.

Dropbox is one of the biggest names in online backup and file sync. Its free service provides 2GB of online storage. Notably, Dropbox supports Linux (Ubuntu and Fedora) in addition to Windows and Mac. On the mobile front, Dropbox offers a free application for accessing and managing files from iPhone, iPad, BlackBerry and Android devices. Paid plans start at $9.99/month for 50GB.

SpiderOak is another Linux-friendly option for online backup, sync, file sharing and storage. It supports Ubuntu, Debian, Fedora and openSUSE - in addition to Windows and Mac. SpiderOak's free version offers 2GB storage space, and users can download the software to an unlimited number of devices. SpiderOak released a mobile application for the iPhone this summer, and the company says it will add BlackBerry, Android, and Windows Mobile 7 support in the future. Paid plans start at $10/month for 100GB.

Zecter's ZumoDrive service lets users access 1GB storage for free - and another 1GB if you complete certain sign-up tasks. It creates a virtual drive on the desktop for syncing files to the cloud. ZumoDrive supports Windows, Mac and Linux (Ubuntu and Fedora), and mobile applications are available for the iPhone, Android and Palm's WebOS platform. Paid plans start at $2.99/month for 10GB.

OpenDrive is for Windows and Macs, and it installs as a virtual drive on the desktop. Its free plan offers 5GB of file storage, but there's a limit of two devices that can run OpenDrive at the same time. Paid plans start at $5/month for 100GB.