These will show you the different MAC addresses the switch knows about.
show mac-address table
sh mac-address address
Another useful one in an all-Cisco environment is
sh cdp neigh
sh cdp neigh detail
This will give you all devices directly attached to the device you are on (and what port on THEM is connected to your device); and the second will also give you the IP address and software release of each of those. Note that this can be disabled (or won’t work) if interfaces have been configured with “no cdp”.