Start backwards search through command history for all commands containing "keyword". Works in bash, and even in ROOT prompt!
Beeps, or rings visual bell, etc.
If your terminal is set up to transmit visual bells, beeps, etc, it can alert you when a long command finishes.
For example:
./run_long_command.sh; echo -e "\a"
You can use many emacs style bindings to delete a word forwards or backwards (Alt+Backspace or Alt+d), kill line (Ctrl-k), and even undo (Ctrl+_). Other useful bindings: