Jake, I thought you nailed it with the expanding gas analogy. Great example . . . oh well
Robb, There's a reason that sentence begins with,
"Over a large scale . . . "
The fact that the universe overall is expanding, does not rule out two nearby objects from moving towards one another.
When you inflate a balloon, the speed at which two points move away from each other is in proportion to the distance between them. Two adjacent points will separate at half the speed of two points that are twice as far from each other.
The 'attraction' between objects due to gravity is inversely proportional to the square of the distance. This means that two identical objects placed twice as far from each other would only 'feel' one/fourth the acceleration of gravity.
Two galaxies can be close enough to each other that the rate of expansion of the universe is insufficient to overtake the attraction of gravity. It is only "On a large scale . . . " that it becomes readily apparent that the separation between more distant galaxies is increasing as the rate of expansion becomes more evident and the motion of galaxies through space becomes comparatively less significant.
I suppose that until you have done it, the motion of galaxies within the expansion of the universe (or of particles moving relative to each other within an expanding cloud of gas) can be difficult to visualise. Can anyone else think of something more available to common experience to relate this to???