Yes, its possible to book at the last hour , even on a holiday weekend. Some travel booking sites such as Expedia or Kayak, have last minute categories that help you book anything: Kayak last minute .You can even call hotels on the same day and ask for what is available , and you can get last minute “rack rates”. By calling the hotel directly , the manager will always accommodate rather then have empty rooms. There are some websites that specifically book for last minute ,usually only within a 2 week window. I have used this site (that was under a former name), it gave us a great deal:last minute travel