If security is a big concern for you, consider encrypting your data before sending it to the cloud. The easiest way to do this is to use , an encrypted cloud-backup service that lets you back up specific files to the cloud and then sync them across multiple devices.

Another option is to encrypt your data locally before storing it in Dropbox, SkyDrive, Google Drive, or any of the other cloud services. Mac users should read Macworld's tutorial on using OS X's built-in Disk Utility. You can also try the open-source program TrueCrypt for Linux, OS X, or Windows to encrypt personal files you want to send to the cloud; check out to get started.

If you have files spread across a number of cloud storage accounts, such as at Amazon S3, Box, Dropbox, Picasa, SkyDrive, and SugarSync, look to . Through this service, you can connect them all, and then drag and drop files between your various cloud providers, no file downloading necessary. It works on almost any browser, including on mobile devices. Otixo is free for up to 250MB of bandwidth usage each month, or $10 for unlimited access to the service.