When going on a road trip or just commuting daily, data plans and data connections are limited. Assuming you will always have access to 3G, 4G, or Wi-Fi is standard in urban areas but uncommon in tunnels or in the country. These are my recommendations for apps I use on Android to entertainment myself when commuting or taking road trips.
I like the ease of RSS pushing updated content to me. Feedly is a great RSS combiner and its interface is great but it does not download content offline. That is where gReader is the best. Through its preferences, you can have gReader sync both ways with Feedly while is automatically downloads the articles you want with images for your offline access. It will delete the articles when you are done.
Both Amazon Music and Google Play Music let you download legal music to your device. Amazon will let Prime members add Prime music (songs, artists, playlists) to their Library and then download it. They also allow uploading 100 songs to the Amazon Music Library for free. I have not used Google Play Music but I know that users can upload more of their own music for free and then can download that music via downloading albums.
Amazon Instant Video now lets Prime users download content TV shows and Movies from their collection. I have found the HBO shows are fun to watch.
TubeMate is for downloading YouTube videos. Use this with Feedly/gReader to get your videos instead of subscribing and being emailed. The downloads are quick and easy and you can select the quality of the videos you want.
Flud for torrents.
HERE is seemingly the best way to download maps for offline navigation. I believe it is inferior to Google Maps but downloading the maps for offline access lets you search for restaurants and businesses when you have limited Internet connection. Keeping some maps on your phone for emergencies is also a good practice.