Music
Almost everyone who runs for very long will at some point want music (or other listening pleasures) to accompany them during their runs, especially for long runs
Certainly every persons’ music interests can vary widely, and even the same person can have different playlist preferences depending on the type of run (intense or relaxing) or mood someone is in.
Playlists
Here is a link to my personal short list of favorite running songs for during a race or a long, intense run.
Check out Spotify to listen to a variety of playlists.
Check out Your World Within for some motivational playlists.
Songs by Beats Per Minute
There is also a theory that the best pace to run is 180 strides (steps) per minute. To accompany this theory, here is a list of songs, by genre, that have 180 beats per minute (BPM).
You can use the BPM site to choose songs of any number of beats per minute. For example, you could choose songs for your playlist that are 90 beats per minute, and plan to take two steps for every song beat.