This new add-on by Johnny Matthews stores selections of objects, making it super easy to restore them later.
It's been a while since I've created a blender add-on, but some discussion on the #blendercoders channel prompted me to dig back into Python and create this: Selection Sets.
It is a quick way to create ad-hoc groups of items that can be reselected easily. Simply select some items and choose the plus button to add a new set. The items in the set are then displayed below.
Click the Cursor select button to select the objects in the selected group. To add more items to a group, select the group, then select more objects, then click the + in the lower list. You can also remove objects from a group in the lower list. This is a very early release (hence version 0.1) but I feel like it is already useful when Blender groups are too heavy handed.