There are a lot of options on this front. As far as I can tell, most displays for embedded platforms are sold as modules that you interface with via a serial or

There are a lot of options on this front. As far as I can tell, most displays for embedded platforms are sold as modules that you interface with via a serial or parallel bus. There are libraries out there to handle the grunt work, if you don't want to dig through data sheets yourself. If you want something that doesn't use any dedicated hardware, interfacing with analog displays (e.g. NTSC/PAL/VGA) can be done with a handful of resistors on GPIO pins. Conceptually, it is easier but actually dealing with timing is a pain. Again, libraries that deal with the grunt work are available.