I found this information useful while working my way through the Erlang in Practice screencasts. All of these apply in the interactive shell (erl).

Find the Erlang version you’re running:

erlang:system_info(otp_release).

To clear a variable/binding, so it can be used again:

f(variable_to_clear).

Show all the running erlang processes:

erlang:processes().

Find more useful tips from Joe (such as how to ping a node with a dash in the name).