One of the most famous free services is Dropbox. It allows you to store and share information with others online. Personally, I'm not a big fan of Dropbox. Many features require you to install the Dropbox program on your computer, rather than just using a browser. Also, the free account provides a measly 2 GB of online storage. That's fine for a few documents or an occasional stored file. But if you've got lots of music or pictures, forget it. There are better options.
My favorite storage location for years has been Google Drive. With Drive, you get 15 GB of free storage space, although this space is shared with your email as well. You can upload files, share them with specific people, or even make them public. Everything can be done through your browser, although Google also has a program to let you sync your files with a PC or tablet. Shared access is easy across Windows, Android, Apple, or pretty much any OS that will support a standard internet browser.
Most common file types can be viewed on the site, as well as downloaded. You also have the ability to create files directly in Drive (which don't count toward your 15 GB limit) but since we're just talking about shared storage today, I won't get into Drive's many great online editing features. For me, Drive is quick, clean, and easy to use.
Occasionally Google offers incentives that permit you to increase the limits on your free account. Be alert for these and take advantage of them. Try out a new product and get a permanent increase in your storage limit. As a result of special deals, I have 25 GB of space on my fee account.
Google also has a separate site for photos, which tend to take up much of your online space. Google Photos allows you to store and share your photos. The great benefit of this is that you get unlimited free space for photos and video.
Some have criticized Google from limiting the size of photos that you can store there. But the limit of 16 megapixels (and 1080 for HD video) is actually a higher quality than most people can take on their phones. The limit really just prevents professionals from storing super high quality photos online at full size. If you need that, try flickr which gives up 1 TB (about 1000 GB) of space which you can use for storing photos of any size. But most of us will be happy with Google's unlimited storage for reasonably sized photos.
Microsoft is starting to become a serious player in free online storage as well. It's free Onedrive account (formerly known as Skydrive) provides you with 15 GB of online storage. This quickly doubles to 30 GB if you install an App on your phone to upload photos. Keep in mind you don't need to use that extra space for photos, just sign up for the app, and use the space however you like. You can get another 5 GB by recommending other users to sign up, at 1/2 GB per user that signs up under your recommendation. Again, keep a lookout for other special deals that occasionally let you expand your free space permanently.
Another reason I like OneDrive is the ability to map a drive letter on your computer to your OneDrive account. If you are interested in doing this, follow this link. I find this to be a great convenience for many programs and utilities that required a drive letter, as opposed to some network connection without a letter. It makes it easy to use LibreOffice directly with your online files.
There is also a way to add a drive letter to Google Drive, which you can find here, but it really is a little convoluted. It's also not really mapping to the drive. It syncs your data to your hard drive and maps to that. The MS OneDrive option is much better, although it only works with Windows 7 and higher.
Expanding your space
I find the shared storage space more than adequate for my needs. I don't want to store everything online anyway. But there are ways to increase your space without paying. First, as I already mentioned, stay alert for incentives that give you permanent increases in space. As the MS-Google competition heats up, there may be more of these. Second, you can always create a second or third free account. Upload your data in that account, then share it with your main account. You have access to all those files from your main account, but they don't count toward your limit.