Dropbox is a cloud-based data storage service which synchronizes with data files on your computers. The Dropbox folk provide 2GB of free storage but if you need more you can sign up for a 50GB or 100GB subscription account.
I prefer Dropbox over similar services because it's transparently simple to use and it employs Alpha sync—more about that below. Save the files you wish to sync in the Dropbox folder on your computer and they're immediately and automatically updated on Dropbox's servers whenever you make changes.
Switch to a different computer (Windows, Mac, or Linux) and your data are automatically synced as soon as you go online. This is an outstanding service and it's completely changed the way I work with data. I no longer need to mess around with synchonizing machines with SyncBack when switching between desktop, laptop or netbook and there's now no necessity to have both synched machines running simultaneously.
The full story
Because it's very easy to manage I use Dropbox for all my everyday working files—the ones that I access and/or change regularly: files like my "fridge door" action file, computer installation logs, inventory, website pages and blog files and notes. I also throw in scanned copies of important documents and photos. The nice folk at DropBox give you 2GB of free storage and it's a no-brainer to install and use.
As long as you don't get carried away with lots of big images, or video and music files, 2GB is a lot of space.
Set it and forget it. Dropbox works seamlessly in the background without any input from the user.
Synchronises your data automatically between all your computers and the online storage.
2GB of free storage.
If you need more: 50GB or 100GB paid storage at US$10 or $20 per month.
The big plus for many users, it's compatible with Windows, Mac and Linux.
Unlike competing cloud services, Dropbox uses Alpha synchronization. i.e. When a file is changed, Dropbox doesn't upload the whole file, only the differential data - the part of the file that's changed.
With large files this is a very big plus.
Less storage than some other free services. For me, that's far outweighed by the synchronization capability.
It's restricted to one location on your computer. This annoys some users, but if you just treat it in the same way as Windows XP's Documents folder it's no big deal.
I understand that this may be changed in a future upgrade.
When you download and install DropBox it creates its own folder on your hard drive. By default, in Windows, the folder is created in your Documents folder but during installation you can move it elsewhere if you wish. The DropBox folder can be used just like any other: add files and sub-folders to your heart's content and DropBox will toil away in the background uploading a copy of those files to their servers.
Every time you subsequently add, delete, or modify files or folders in your DropBox they're immediately updated on the remote site.
It gets better!
If you use more than one computer you can install DropBox on each of them, log on to your DropBox account when prompted and it will automatically download your current files and subsequently update them with the latest changes. Thenceforth, whenever any of your DropBox machines are connected to the web they will automatically be synchronised.
If you don't have access to your own computer you can log on to your online account at Dropbox's web site from any web-connected computer in the known universe and access your files.
You can use DropBox on Microsoft Windows, Mac OS X, or Linux computers.
For text, pdf, Word and Excel files 2GB is a lot of space, but if you really like DropBox (what's not to like?) and you wish to have more storage—for lots of photos for instance—you'll need to purchase a 50 or 100GB account as mentioned above.
Synchronizing program data files
With many software programs, the default location of the data files can be changed to a folder of your choice. If you put these folders in a subfolder of Dropbox on each of your computers, those data will be kept up-to-date and in sync. This works very well with programs like Autohotkey, Tomboy Notes, Info Select, Wiki-on-a-Stick, PhraseExpress, Stickies, and no doubt many others.
There's a Public folder in your Dropbox. Each file that you place in the Public folder is given its own unique URL which you can paste into emails, web pages, etc to allow others to read it. Dropbox-logo.png