Tool that scans IP ranges looking for computers sharing resources through samba/netbios , and let you directly access them if non password is set. If a pass is set, then you can try to brute force it.
SMBScan has no usage limitation. There are other samba resources scanner, but they are really huge, or have some functions restricted unless you pay for them.
Remember, you need to install the Microsoft Networks Client in order
to access shared resources.