Blender adds new objects in XY plane ,however if one is working in other planes(eg. XZ,YZ etc), this can be quite irritating having to transform the object to the desired view everytime a new object is added .Is it possible to add a new object in the visible plane?
If you select Align to: View in Preferences, new objects will origin to current view, not world:
But if the view is not top/bottom/side (rotated using MMB), object will be rotated in same direction as a view point.
You can also adjust last operation and set align to view here:
From the 3D view-port open the object properties (N),
scroll down and expand 3D Cursor, the Z: axis value can be entered from here and your objects will be added to the new location.
When typing values switch between X: Y: and Z: with (Tab) and (Shift+Tab), or just scrub with mouse over them.