I wouldn't read too much into short-term numbers.  We all talk about how inelastic gasoline demand is in the short run.  Well, we're still quite clearly in the very short run.  

If you want an indicator of how spooked people are by gas prices, wait for the first few days of October, when the car sales figures for Sept. come out.  I've seen a few sporadic reports (without actual numbers) saying that sales of SUV's and pickups have flat-lined.  If this is true, and if the numbers show people moving to smaller vehicles, then we have a strong indication that drivers are actively looking for ways to conserve fuel.

Personally, I expect to see sales WAY down across the board (more so on the less efficient models), as people will be scared enough by price volatility to avoid making a major vehicle purchase or lease.

Lou--will you remind me/us of this if I don't remember to post it come October?
This is a very good point, and is probably true.  One thing that really caught my eye is Bill Ford, Jr. this past week calling for an automakers/US gov't summit about promoting fuel efficiency.  Now I don't know if he had that on his agenda for a while, but the timing is interesting, especially given the reports that US automakers are grumbling over the Japanese "hoarding" hybrid parts (read: efficient batteries).  I wonder if Ford, GM, et al., have read the handwriting on the wall in their sales figures and have decided the SUV is finally dead.  Problem is, US auto plants are all tuned-up to produce SUVs, not hybrids, or even more economical conventional models.  The motor city will really be hurting, whereas I think Toyota and Honda stand to make record profits here.
This still comes back though to the question of what happens to the SUV that is sold as used on the market.  Yes the price is depressed, but it is still out there, and people would still be driving the damned things.

It is only when their value to the scrapyard exceeds what anyone might pay for it that we would see a marked improvement.

One other observation though.  Getting a Prius is tough - they just don't make enough of the things, they are expensive, and they haven't been around long enough for people of more limited means to be able to afford a used one.

Diesels are tough to get too - realistically VW is the only one worth having unless you want a big diesel pickup or SUV, but at least these have been out there for a longer period and getting used ones isn't as tough as it would be for a used hybrid.

There are however quite a number of cars out there that get > 30mpg.  By my standards, not great, but if you are moving up from an SUV it would be a pretty good deal.

I have a friend who is really into Vespa scooters, and he just bought a Honda motorcycle so that he has something more suitable for highways.  He was telling me the other day that it appeared to him that there might be more people on scooters out there.

I hear anecdotal stories about people simply moving closer to work.   You wouldn't really be able to tell by looking at the roads.  There is a guy at work who drives a Fornicator, but he only lives 5 miles from the office.  He could practically walk to work if he wanted to.

Adding to the anecdotal stories: I have taken to consistently driving under the speed limit (I am now normally going 50-55 mph on the freeway) and it is my observation that I still feel safer (i.e., not as many people are flying past me) than I would have two years ago driving at the speed limit. I think that people are slowing down, at least a little, and I think this may have something to do with the price of gas.