civilization-5
When you first research a technology that reveals a new resource on the map (eg. Electricity reveals Aluminum), you can click the tip that comes up to center the map on deposits of that resource that are near your cities.
Is there a way to easily find those Strategic Resources again on later turns? So far I haven't found any method other than hovering my mouse over all of the tiles near where I thought it was to try to locate it.
The diplomacy summary that you get from clicking the scroll in the upper right will show you all the civs and city states at once, as well as what resources they have available, how much gold they have, and how much gold per turn they are making.
I highly recommend the "Luxury Resource Display" mod. It's one of the higher-ranked mods at the moment, for good reason - it makes you permanently just a mouse-hover away from seeing a detailed list of how many luxury resources you currently have of each kind, including how many are traded.
Just search for it in the in-game mod hub, it's easily found, but it seems to also be downloadable from here (I recommend the in-game method, though).
Best Answer
You can turn on the "resource icon" overlay which will put up floating icons showing what all the resources are (Ctrl+R, or click on the "toggle map options" button to the left of the mini-map and tick "resource icons").
If you then zoom out you should be able to see where the resources are quite easily, and what they are.