On our site, new listings are marked on the map with an orange marker and on the right side list with a corresponding orange banner that says "Fresh". These listings are posted to our site almost as soon as they are posted to the internet, and remain marked as fresh for 24 hours. The orange marker disappears naturally after 24 hours, or after you click the listing so that you know it's been viewed.
You can receive email alerts when new listings come on the market by clicking the "Get alerts for this search" button on the top of the map page. You can adjust the frequency of the emails as you wish.