Starting today, you can get triple points on all Hertz rentals through the end of the month (September 30, 2013). The one major caveat to this promotion is that you must have registered for this promotion prior to booking your reservation. If the price has not yet gone up on an existing reservation you already have during the month of September, you definitely should re-book.
While triple points is great, keep in mind though that Hertz is increasing the number of points needed for a free rental starting in October. You can read more about it in this prior blog post.