Have you ever needed to sync files between two or more machines?
Have you wanted to also have an off-site copy of those files?
Have you needed to sync files between Windows and Macintosh machines?
Have you wanted to have a public photo album to share pictures with your friends and family?
Have you needed a shared on-line file repository for collaborating with co-workers?
Well Dropbox can do all this for you. Dropbox is a relatively new service that is currently in beta that allows you to "store and share files online."
After installing the Dropbox application on one machine, you create an account and link that machine to the account. Then, any file that is placed in the My Dropbox folder (which in Windows lives inside the My Documents folder) gets automatically synced with your Dropbox folder on all other linked machines.
If you only have Dropbox installed on one machine, it becomes an off-site backup service. Dropbox uses Amazon's S3 service behind the scenes to house your data. So files placed in your Dropbox folder are automatically uploaded to the Dropbox servers. Should you delete them on your local machine or suffer data loss, they can easily be retrieved from the Dropbox servers by installing Dropbox on a replacement machine, or directly from the Dropbox website.
The real power of the service comes when you add more machines to your account. Every linked machine keeps a synced copy of the files providing redundancy and the flexibility to modify any file on any machine and have the latest version be available everywhere. No more carrying around a USB drive, emailing files to yourself or wondering who has the latest version of a file. Dropbox is not a true peer-to-peer service, which is a good thing. Files are synced to and from the Dropbox servers and each machine receives the latest changes as it comes online, so you don't have to leave machines on all the time in order for them to receive updates.
Dropbox also supports shared folders that allow anyone you invite to the folder to have access to the files in that folder. This is a great way to collaborate and share files with coworkers. There is also a folder specifically configured to hold photos. Any images placed in there are automatically turned into a photo album with a publicly accessible URL you can give out. There is also a Public folder that is accessible to anyone (I think anyone at all, not just any Dropbox user).
So be careful how you use that one!
There is also a web interface that allows you to access files on machines that don't have Dropbox installed. You can also access previous versions of files from the web interface. So when you screw up that file and need to go back to last week's version, you can do that.
There is a short video on the website that gives a very good overview of what the service can do.
I've been using Dropbox for about a month and have found it to be a very powerful service. The developers are very responsive and working hard on new features and do seem to squash the limited number of bugs that have cropped up very quickly (sometimes within hours). They also seem to be committed to refining the service as they have described it. Forum posters often suggest adding unrelated features, which the developers will often (politely) dismiss as something they are not planning on implementing anytime soon.
I have used Dropbox with numerous small and a few very large files (Linux ISOs). It handled both equally well, but the upload speed on the large files seemed slower than it should have been. I didn't really investigate where the bottleneck was but I experienced it on two different connections. Of course, moving 700 Megs of data over just about any connection is going to be a time-consuming operation. However, small files are uploaded very quickly and available to everyone immediately.
One thing to note, is that the My Dropbox folder is just another folder on your machine. So if you copy files into it in order to sync them, you will be creating 2 copies of the data on your local machine, and using up twice your hard drive space. The developers are working on resolving this problem by implementing watched folders and/or some type of symbolic links. Local hard drive space is abundant and cheap, but it is something to be aware of since you are creating multiple unsynced copies of the data, which is exactly what Dropbox is trying to avoid. If you can, your best bet is to keep the only local copy of the data in the My Dropbox folder.
When the service is rolled out Dropbox plans to offer 1 Gig for free with plans for more storage, but pricing has not been determined.
The AdmiN and I have an extremely limited number of invites available. If you are interested leave us a note in the comments. (EDIT: AND BE CONVINCING ABOUT IT!)