Once in a while I will issue a command that takes longer than I had thought it would (archiving a directory or something). How do I escape the process, send it to the background, and return to the prompt? I think there's a keyboard shortcut, but I can't find it..
If you're using BASH, just press CTRL-Z, which will suspend the process, and then use the
bg command to send it to the background. If you want more detail have a look at this article on BASH job control.