A: 

Fuse won't work on Windows.

My choice would be:

  • FUSE for Unix/Mac
  • Eldos Callback List or Filter (we're currently using Filter) for Windows (http://www.eldos.com/)

Regards

A: 

Jungle disk

Laserallan
I'm not looking for implemented solution but a way to implement the solution
Goran
+1  A: 

VirtualBox' VDI. It's Open Source.

vartec
VirtualBox is a whole virtual machine, not just a virtual disk. To answer the question, you'd need a guest OS serving SMB, WebDAV or something like that. And that would be a pretty big waste of disk and performance.
Chris Dolan
A: 

What about simple FTP? Or NAS? Stick with a standard protocol and you shouldn't have any problems integrating with it. I wrote a Linux SFTP filesystem extension once Back In The Day, but with most OSes supporting user-mode filesystems nowadays, it shouldn't be too hard to integrate with whatever you might choose.

TMN
+6  A: 

A simple solution is to use the native SMB client for each of your target platforms, then use that to mount a custom Samba filesystem implemented using Samba's VFS API. Custom NFS servers have been used to implement cross platform Unix virtual file systems, but SMB is a much better choice to support Windows and Linux.

If you need the VFS to access client-side resources, you must run the Samba server with your VFS on the client and then use a loopback or localhost network to mount the drive. Samba is widely ported including a port to Win32 using Cygwin as an adapter.

Ken Fox
This is as close to an answer as I got. Still no simple solution exists so I guess we're back to reinventing the wheel.
Goran
+4  A: 

WebDAV. In a heartbeat. It's cross-platform by nature, and there's a substantial amount of client support, as well as decent open source server code. Apache mod_dav is your friend.

Check out WebDAV client support on Mac, Windows, and Linux:

Open source WebDAV servers:

And don't forget to look at WebDAV resources.

Anirvan
I wrote a custom WebDAV file system and supporting all the various buggy clients is a huge task. My company eventually limited support to just a few clients (Windows web folders, MS Office) that had bugs we knew. If I did it again, I'd write a Samba VFS plug-in.
Ken Fox
A: 

Microsoft Live Mesh will give you synchronized folders across Windows, Mac, your online Mesh storage, and Windows Mobile phones.

David
You're missing Linux.Also, Microsoft and cross-platform do not go hand in hand.
LiraNuna
+2  A: 

I use jungledisk on all of the mentioned platforms to backup and share files. If you look at their download page, you'll see all of the platforms it's compatible with. I backup my webserver (CentOS x64), a mac OSX 10.5, and a dual-boot pc (Vista/Fedora) all under one license!

  • All versions use WebDav
  • Linux version also has FUSE capability
  • Uses Amazon's affordable S3 storage platform
  • Soon to add Cloud Files support (Mosso) at 15¢/gb no charge for I/O.

JungleDisk

Blaine
+1  A: 

SSHFS (requires SFTP on the host side). There are some bugs with it, but we've had good luck with it overall.

Mitch Haile
+1  A: 

You can use Alfresco JLAN. JLAN is a Java-Client and Java-Server Implementation of the protocols CIFS, NFS und FTP. With JLAN can files be shared over the network, which are available via a network drive.

The download is at http://sourceforge.net/project/showfiles.php?group_id=143373&package_id=248550

Horcrux7