:r file

Read in contents of file after cursor.

:r !command

Read in output from command after current line.

:nr !command

Like preceding, but place after line n (0 for top of file).

:!command

Run command, then return.

!object command

Send object, indicated by a movement command, as input to shell command command; replace object with command output.

:n1,n2! command

Send lines n1 through n2 to command; replace with output.

n!!command

Send n lines to command; replace with output.

!!

Repeat last system command.

!!command

Replace current line with output of command.

:sh

Create subshell; return to file with EOF.

Ctrl-Z

Suspend editor; resume with fg.

:so file

Read and execute ex commands from file.