htop - Undoubtedly the most famous of the top-like tools. It implements some extra options to the "top" command, like colors, ability to scroll horizontally and vertically, and a better interaction with the processes listed.
nethogs - network information, but instead of displaying the traffic by protocol, nethogs shows the bandwidth usage by process. Very interesting.
sntop - Pings a list of hosts and indicates whether they are active or inactive. Must be configured in /etc/sntoprc.
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