Expired1.com is described as 'online app which scan and filter domain list daily to show you expired&expiring domains'. There are five alternatives to Expired1.com, not only websites but also apps for Self-Hosted solutions. The best alternative is DomainTools, which is free. Other great sites and apps similar to Expired1.com are WhoisAPI (Freemium), CubDomain (Free), Complete API (Paid) and WhoAPI (Freemium).
WhoisAPI is the premier provider of freshly parsed whois data for domain names and IP addresses, also providing IP to geolocation, HTML to PDF, and domain availability RESTful HTTP APIs. Billing is performed on a pay as you go basis, free monthly use.