VirtualBox: Accessing host's shared folders from guest Mac OS

To enable shared folder, while the guest OS is running you need to select Devices menu and then Insert Guest Additions CD Image... (Host + D). But, this feature does not support for guest Mac OS. To verify that, in host OS you can browse to /Applications/Virtualbox.app/Contents/MacOS/VBoxGuestAdditions.iso, in my case host OS is Mac OS Mountain Lion, and you will find these files: VBoxWindowsAdditions.exe, VBoxLinuxAdditions.run, VBoxSolariesAdditions.pkg but no *.app file for Mac OS.

There is an alternative way using File Sharing service of Mac OS X. Please follow the steps below.

1). On your host machine, open Network Preferences and then Sharing to share your folder or file:

* Make sure you provide Read & Write access permission on the shared file/folder to everyone

* We gonna share it using SMB service 

2). On your guest OS, open Finder and select Go then Connect to Server... and type smb://10.0.2.2 and click Connect 

Reference
http://www.takwing.idv.hk/tech/virtual/faq/access_shared_folder.html