A bit of a short question that doesn't give any context of where you are trying to do this request or how you want to see the results.
In the UI, you can modify a lot of the tables and boards to show user. If you want to be a more specific, you can use a Custom List app and add it to a page. This gives you a "query" box in the app settings to allow you to filter.
If you are doing this from an app using the SDK 2.0 (which you should be using now and not 2.0rc3), then the 'user' is returned as minimalist object which contains the basics, e.g. Owner.Name. The SDK 2 was changed to not fetch the full objects in this situation, so if you want the complete info on the user, then you might need to do a request to fetch the object as a separate action.