Just Dropped offers a service that allows you to search for domains that just have expired and are now available for purchase. Unlike most domain search services, they allow you to set up some pretty complex search parameters so that you can monitor for newly available domain names that match very specific patterns. If you are in the business of farming domain names, or if there is a specific domain that you are interested in, this service is for you.

While they do offer this domain search for free, you are required to sign up for a user account.