This command is a very little known secret of Samba. It returns IP adresses of all Samba servers in one’s own broadcast domain:
nmblookup __SAMBA__
This one returns a list of all NetBIOS names and their aliases of all Samba servers in the neighbourhood (it does a ‘node status query’):
nmblookup -S __SAMBA__
This one returns a list of all IP adresses of SMB servers (that is, Linux+Unix/Samba or Windows) in the neighbourhood:
nmblookup '*'
Finally, all NetBIOS names and their aliases of all SMB servers (Linux+Unix/Samba or Windows):
nmblookup -S '*'
The command given in the other answer nmblookup -S WORKGROUP does NOT return all Samba or all SMB servers from the neighbourhood. Instead, it returns all servers’ NetBIOS names who happen to be members of a workgroup named ‘WORKGROUP’. The results are independent of the servers’ OS (wether that is Windows, or wether that is Linux/Samba) — and it is a well known fact that sometimes lots of Windows member server are part of a Samba-controlled domain or workgroup. [Yes, it happens that Samba’s default workgroup name is ‘WORKGROUP’… but so what??]. — But the question was ‘How do I get to know all SMB (Samba?!?) servers in my network neighbourhood?’