Serve current directory tree at http://$HOSTNAME:8000/
$ python -m SimpleHTTPServer
Currently mounted filesystems in nice layout
$ mount | column -t
Get your external IP address / host / user agent / port from http://ifconfig.me/
$ curl ifconfig.me
or
$ curl ifconfig.me/ip
$ curl ifconfig.me/host
$ curl ifconfig.me/ua
$ curl ifconfig.me/port
Execute a command at one, given time
$ echo "ls -l" | at midnight
More at https://www.commandlinefu.com/commands/browse/sort-by-votes