Here are some common APIs that are often integrated with real estate websites:

1. Zillow API: Zillow is a popular real estate marketplace in the U.S. By integrating the Zillow API, you can access property data, estimates, and market trends, which can be used to provide valuable insights to potential buyers and sellers on your website.

2. Google Maps API: Integrating Google Maps allows you to display property locations, provide directions, and offer street view and satellite imagery. This enhances the user experience and helps potential buyers easily locate and visualize properties.

3. Twilio API: Twilio is a communication platform that enables sending and receiving text messages and phone calls. By integrating Twilio, you can set up automated notifications, reminders, and facilitate communication between agents and clients directly from your website.

4. Calendly API: Calendly is a scheduling tool that simplifies the process of booking appointments. Integrating Calendly allows potential buyers to easily schedule property viewings or consultations with agents directly from your website, streamlining the booking process.

5. DocuSign API: DocuSign is an electronic signature and document management platform. By integrating DocuSign, you can enable digital signing of contracts, agreements, and other real estate documents, making the process more efficient and convenient for all parties involved.

6. Salesforce API: Salesforce is a popular CRM platform that helps manage customer interactions and data. Integrating Salesforce allows you to sync leads, contacts, and deals between your website and CRM, enabling better tracking and nurturing of potential clients.

7. Mailchimp API: Mailchimp is an email marketing platform that allows you to create and send targeted email campaigns. By integrating Mailchimp, you can capture leads from your website, segment them based on interests, and send personalized email campaigns to nurture them.

8. HubSpot API: HubSpot is an all-in-one marketing, sales, and service platform. Integrating HubSpot enables you to manage leads, automate marketing tasks, and track website analytics, providing a comprehensive view of your marketing efforts.

9. Walk Score API: Walk Score provides data on the walkability, bikeability, and transit accessibility of a given location. By integrating Walk Score, you can display this information for each property, helping potential buyers assess the convenience and livability of the area.

10. Yelp API: Yelp is a popular platform for local business reviews. Integrating the Yelp API allows you to display nearby amenities, such as restaurants, shops, and services, for each property listing, providing valuable information about the surrounding neighborhood.

11. IDX (Internet Data Exchange) API: IDX is a system that enables real estate brokers to display MLS (Multiple Listing Service) listings on their websites. By integrating an IDX API, you can showcase a wide range of property listings directly on your website, providing a comprehensive search experience for potential buyers.