Amazon Cloud Drive

Prices vary
Amazon Cloud Drive's online storage is pure and simple. Its most recognizable feature is the ability to play MP3 or AAC music files directly, via Amazon Cloud Player, which is technically sold separately. A free account with Amazon gives you 5GB of space for files, plus the ability to import 250 songs to the music player. More file space is available starting at $10 per year for 20GB, and you can separately choose to upgrade to a Premium music subscription (250,000 imported songs) for $24.99 per year. For music, it's great, but for file-syncing, we think some of the other options are preferable. Read the full review ››

Apple iCloud

Free to $100 per year for 100GB; additional $24.99 per year for iTunes Match
iTunes Match basically scans your music and, if it has a match of a song, it gives you license to download or stream that song from its servers at any time, meaning you can delete files from your computer (which is something you can't do with basic file-syncing, where files are generally hosted first on your computer and only synchronized through the cloud). Read the full review ››

CX

Free (10GB) to $19.99 per month (100GB)
It doesn't have a big name, or even a very long one, but CX offers more free storage than any of its competitors: a whopping 10GB! That will be reason enough for many users to snap up an account. CX also has a very elegant online dashboard that I like even more than its downloaded software for both Mac and Windows, which might make it ideal for people who used shared computers frequently (computer labs, Internet cafés) and can't always install software locally. Read the full review ››

Dropbox

Free (2GB) to $19.99 per month (100GB)
Dropbox is ideal for working with files that you want store in a single folder. The Dropbox mantra is, "Put it in the Dropbox folder, and it will sync." However, Dropbox does allow you to set up entire sub-folder structures, if you'd rather, it's just not how the developers envisioned the service in its earliest days and hence is seen as an advanced option. When used as intended and designed, Dropbox is dead simple. There are versions for Windows, Mac, Linux, iOS, Android, and BlackBerry. The downsides are that you only get 2GB space with a free account, and Symbian and Windows Mobile operating systems are not supported. Read the full review ››

IDriveSync

Prices vary
IDriveSync is a free file-syncing program, but it becomes most appealing when you need a lot of space for a little money. The free account gives you a modest 5GB of space, but a Pro 150 account offers 150GB of space and unlimited device installations for only $4.95 per month. For even more space, you can upgrade to a Pro 500 account: 500GB for $14.95 per month. Like most other file-syncing services, IDriveSync installs locally on any of the following devices: Windows PC, Mac computer (OS X 10.5 Leopard or later), Apple mobile devices running iOS 4.0 or later, and Android devices running version 2.1 and later. With IDriveSync, you can either use a new folder that the system creates for you, or select existing folders on your machine that you will have synced. Read the full review ››

Microsoft SkyDrive

Free for 7GB to $50 per year for 107GB
Offering a generous 7GB of free online storage, SkyDrive is Microsoft's answer to iCloud, though it actually predates Apple's service by several years. Unlike iCloud, SkyDrive offers a Web interface and online office apps for all your cloud content. The service has recently annexed Microsoft's syncing capability formerly available in Windows Live Mesh, and the syncing even works between Macs and PCs. SkyDrive not only serves as online storage accessible from PCs running Windows 7 or 8, Macs, iOS devices, Android devices, and Windows Phones, but also serves as backup for the Windows devices' settings and personalizations. A unique "Fetch" option lets you remotely retrieve files from a PC even if they were never uploaded to SkyDrive. Read the full review ››

SafeSync for Business

Prices vary
File-syncing isn't just for individuals. Small to medium businesses, and even enterprises, have learned that file-syncing services can replace FTP servers, some types of email collaboration, and can make working with outside contractors a much simpler affair. Business-level file-syncing usually comes with a strong security guarantees, and that's where TrendMicro's SafeSync for Business hits its mark. All your organization's data is encrypted with bank-level security during syncing. The software works on Windows, Mac, Android, and iOS. It has a business-like, no-nonsense interface, and very good sharing functionality, with controls for who can view or access which files and for how long. Read the full review ››

SafeSync for Home

$23.95 per year (20GB) to $89.95 per year (100GB)
Security company Trend Micro also has a file-syncing service for home use: SafeSync for Home, which puts privacy and security first, and as a result does not offer a free plan. For an annual cost of less than $25, you do get a huge patch of server space, 20GB, which can house a lot of data. SafeSync has good sharing features that still think about how security factors into the equation. The interface isn't sexy, but the service is very reliable. Read the full review ››

SugarSync

Free (5GB) to $14.99 per month (100GB)
File-synchronization service SugarSync offers a generous 5GB cloud storage space with a free account. By far the most intuitive of all the products we've tried, SugarSync is a breeze to use across all major operating systems: Windows, Mac, Linux (in beta), Android, BlackBerry, iOS, Symbian, and Windows Phone. When you install the software on a computer, it adds a right-click function that allows you to quickly mark any file or folder to back up, which is immensely useful. SugarSync's one downside is that it has exhibits some quirks and hiccups when deployed across multiple desktops, but it's exceptionally good if you have one primary computer and a few mobile devices. Read the full review ››

Syncplicity Business Edition

Prices vary
Another provider of business-level syncing services is Syncplicity, whose Business Edition supports integration with SalesForce, SharePoint, and even Google Docs. Syncplicity offers its business clients automatic back up, access to older versions of files, and very secure mobile access, as you can remotely wipe data from a lost mobile device to protect your organization's information from getting into the wrong hands. All mobile data is encrypted while both being stored and while in transfer (i.e., while uploading). Read the full review ››

Syncplicity (Personal Edition)

Free for 2GB to $15 per month for 50GB
Similar to SafeSync, Syncplicity also touts its strong security measures and puts a price on its syncing service ($15 per month for 50GB), although it does have a free option that's equal to Dropbox's: 2GB. If you use sites such as Picnik, Zoho, Scribd, and iPaper for editing files, Syncplicity might be appealing for its integration with those services. Like SugarSync, Syncplicity has a right-click-to-sync function. There's no support yet for Linux, Symbian, BlackBerry, or Windows Mobile, and the interface is a little clunky. Read the full review ››