Type smbclient -L -serveripaddress and now you can see what folders are shared. Then you can mount the desired folder with:
sudo smbmount //serveripaddress/folder localfolder -o username=youruser,password=yourpassword ,uid=1000,mask=000
There is, also, a small graphic soft to browse smb networks: pyneighborhood. It's a GTK2 application that runs very well. It can be installed from the Synaptic package manager.
More infomation on this thread at the Ubuntu forums.