How to run programs from a linux terminal without blocking the terminal?

When I start a program from a terminal I can't use that terminal instance again until I close the program.

Is there a way to execute a program/application from a terminal without blocking the terminal until the program ends?

You are looking for job control which is supported by most shells. See this article for an introduction. At some point you might also want to read the official documentation for bash which is the default shell in Ubuntu.

In short: To start a job automatically in the background put an & after the program call

$ program &

You can also stop programs with CTRLz and then put them into the background later with bg

$ program
^Z
$ bg

To get them to run in the foreground again use fg.

In Ubuntu 16.10 I can't get the ctrl + Z thing mentioned in an other answer to work, but

program &
^C

Does work for me, in other words, ctrl + c after you start the program with a trailing ampersand.

If job control isn't exactly what you want, look into screen.

Screen controls multiple virtual terminals so you can run multiple programs without them interacting with each other. For example, you can run mocp (a music player), aptitude (a package manager), and vim (a text editor) simultaneously, even though all are interactive programs which treat the terminal as if they had sole access.

This makes it easy to switch from one task to another, such as creating a new terminal within screen to read a manpage – without losing your place elsewhere – flipping back and forth, etc.