Mac OS X 10.6.x:
Add this line at the end of /etc/auto_master
with the following content:
/Volumes/mount1 -fstype=smbfs ://user:email@example.com/share1
/Volumes/mount2 -fstype=smbfs ://user:firstname.lastname@example.org/share2
Where everyline is a mounted SMB share. Replace "/Volumes/mountX" with folders on which you want to mount your Samba-Shares. Replace user, passwd, IP and shareX with the information of your SAMBA Server.