How can I find my units in Civilization 5?

Solution 1:

In the unit overview (selectable from the top-left button), you can either double-click a unit - to select it and center your view on it - or you can click a unit and then, in the lower-left unit info box, either click its portrait or its name.

As far as I know there is no way to get an immediate overview of where all your units are, which is a shame - I would also be interested in something like that. They don't even appear in the mini-map in any form until after you select them...

You can find more information about the unit list (for example, what do the colors mean) in my answer to another question.

Solution 2:

You can also use the new strategic view. Among the many overlays available for it is one that shows an icon for each unit (for ease of use, you might want to disable the other icons and overlays), and you can easily scroll out far enough to see your entire empire. I believe you can even control your units directly from that view.