Create Ubuntu Shared Folder in Virtual Box

Shutdown your VirtualBox Ubuntu session if it is running

In your host operating create the folder you want to share - e.g. ubuntuShared

From the VirtualBox control panel, click on your Ubuntu Virtual Machine

In the right hand panel, click shared folders

A window will open to manage shared folders. Click the add folder icon on the right hand side

Navigate to the folder you created in your host operating system and click choose

Click ok to close the navigator window

Ensure that your selected folder is highlighted in the shared folder panel and click ok

Start your Ubuntu session and log in

Open a Terminal session (Applications->Accessories->Terminal)

Create a mount-point directory for your Shared Folder - e.g. sudo mkdir /media/windows-shared

Mount your shared folder over your newly created directory - e.g. sudo mount.vboxsf ubuntuShared /media/windows-share

http://developer-repository.blogspot.com/2008/12/create-ubuntu-shared-folder-in-virtual.html