To back up, sync and share your computer files, you can check out Dropbox, SugarSync, SkyDrive and some other free cloud storage services, as mentioned before.
Now, there is a new cloud storage service — Google Drive, which is a Google product, and that's why all the existing competitors should be worried.
Comparing to the other cloud storage services, Google Drive offers 5 GB free storage, which is not the biggest nor the smallest, but it does have the following 3 advantages:
1. 2-step Verification
If you have enabled 2-step verification for your Gmail, you also need to enter the password as well as the verification code to log in your Google Drive, which is the most safe way in the world up till now.
2. Google Docs Combination
Your Google Docs will be integrated into Google Drive, which means that besides to back up, sync and share your files, you can also easily edit your documents, and even use the OCR service to extract the text from an image.
3. Sync Preferences
As default, all your Google Docs files will be synced, but which you can disable, and you can also only sync the files in some folders.
The above 3 features make Google Drive a good cloud storage service, but if you disconnect it, you will be required to download all your files again when you sign in next time, which is not good for convenience, nor security, since anyone who gets access to your computer can empty your Google Drive folder and delete all your Google Docs files that are synced.
By the way, Google Drive is still on beta stage and you need to apply for an invite to join it, good luck and have fun!