Sharing a folder via SMB (the so called Windows Sharing) with OS X is easy. But username and password were always required. I wanted to make an anonymous share and didn't know how.
Sharing is done like this:
One can see the Everyone user added and still a password was required to log in. Accidentally I found the fix for that.
I had to enable the guest user for file sharing:
That's it. Problem solved.
NOTE: The guest user is disabled by default in OS X Lion. You'll have to enable it first.