Yes, Its possible.
As mhku suggests, the easiest way to do it is by installing Samba. Its available for instalation throught the blue panel in most images.
Once installed you'll have to modify the config file to suit your needs. The file is called smb.conf and will be stored under either /etc or /etc/samba.
Here is my config
Code:
[global]
load printers = no
guest account = root
log file = /tmp/smb.log
security = share
server string = DreamBOX network services
workgroup = Dream
netbios name = DreamBOX
client code page=850
character set=iso8859-1
case sensitive=yes
preserve case=yes
short preserve case=yes
[root]
comment = Root file system
path = /
read only = no
public = yes
guest ok = yes
[Harddisk]
comment = Harddisk
path = /hdd
read only = no
public = yes
guest ok = yes
With the above config, when I browse to the dreambox I can see two directories. One of these is to access the file system in flash, the other is the harddisk. You can add as many shares as you like and there are lots of other options you can set. Read the Samba man page for more info.
PS: If there are kids (or adults) in your home who might come accross the shared directories, it would probably be advisable not to make the root file system available via a share. They could wreck things.