> You need to backup some data and you don't have any external media (HD, pen/flash drive etc)
> You wish to share a heavy file over net, with multiple users
> You need to email a file which your email client cannot handle.
> Your web host or blog has limited storage or does not accept upload of certain file formats.
> You wish to organize your photos online so others could view it that way.
What ever the reason may be, there is a solution to all.
I have listed a few sites that provide free online storage or file sharing. Pick the one that's most suited for your need and you are good to go. Although all the sites mentioned here, provide free service, most of them have a storage time limitation. If you wish to store your files for longer duration, I would suggest you go through the site Rules/FAQs for same.
Skydrive (recommended): This offers free storage of upto 25 GB and data that you upload is stored for life. Its a Microsoft product hence you can rely on it.
Box: Free storage of upto 1 GB and file size is 25 MB
Mozy: Up to 2GB free storage. It requires download of desktop application which helps you figure out which files to back up.
DropBox: The interface is user friendly and simple - you can upload up to 1 GB of your files here.
divShare: Upload all kinds of files here, including multimedia. Includes integration with Facebook and WordPress.
MediaFire: Apart from uploading files here, you get lot of extra options like (creating folders, galleries, etc).
Omnidrive: Free online storage of upto 1 GB. It also integrates with Zoho and Snipshot.
Omemo: This basically has a desktop application download, which can pick up portion of you free Harddisk space. It clubs the space from multiple users to create a large virtual space.
Senduit: Need to share a large file with someone? Try Senduit - just upload your file, share a secure URL, and you're all set.
Yuntaa: Free storage up to 1 GB; also offers blogging.
YouSendIt: This is a file sharing system, where you can upload a file of about 2 GB and share privately or publicly.
Megashares: Up to 10GB available for upload storage; you get a URL where your files can either be privately or publicly accessed.
Badongo: The free account gives you Unlimited storage space. You get a user friendly File management system and FTP uploads
Dropbox: Its an installer that creates application folders in your system. The files in these Folders get synchronized automatically and are available online. The free account gives you 2 GB space. Drop your files in application folder and access it on any PC.