This app was mentioned in 4 comments, with an average of 3.00 upvotes
I like to use opencyclemap.org because it shows the roads, but also the trails for biking and hiking. More trails are shown than the official park maps for my area, which is good for hiking, and trails that are bike-able are shown that otherwise I wouldn't know about.
I use an app on my phone that lets me save these 9and other) maps for use without a network connection, so I can see where I am on a map with GPS without using data.
Edit: The app I use is made by Atlogis. I think it's also available for iPhone. It's probably not the only app that can save maps for offline use, just search for offline maps when looking for apps.
If you find yourself roaming parks or trails or travelling where cell signals are faint (or you don't want to use up expensive mobile data) then an app that allows you to download offline maps can be great.
The maps offered by Open Street and Open Cycle tend to show trails that maps such as Google do not. The app I use and recommend is Topo Maps Pro by Atlogis: https://play.google.com/store/apps/details?id=com.atlogis.camaps&hl=en
That's the Canadian version, but there are versions for many locations. There are also free versions so you can try it out. The interface is respectable and one can choose from a long list of map imagery, including Google and satellite. It's helped me navigate trails in parks around me where the provincial government doesn't list them. The GPS pinpoints where I am and then I'm good to go.
I just discovered Canada Maps Pro
It has large topographic map selection as well as route planning and tracking. It also allows for map caching for those times you are in the bush with no reception. Once recorded, the track can be replayed on the map and it displays all the stats of the trip.
There's this for us Canucks:
https://play.google.com/store/apps/details?id=com.atlogis.camaps
I wouldn't bother with the free version, it's pretty limited when you lose reception.