A huge list of public Web services an extract from the list:

• trade shows
• global addresses validation
• Offers a list of learning objects available in Asian Institute of Technology
• Filters spam via web service
• Allows developers to retrieve dates for specific US holidays
• Add Latitude & Longitude Coordinates to your Addresses - Free Trial
• Validate name and address information (24-hour accurate) associated with any telephone number, including residential, business and government numbers.
• Send SMS messages to Italy with delivery receip / Invia SMS in Italia con ricevuta di ritorno
• Query if Yahoo User is Online/Offline
• Lists latitude and longitude for specified city, or state.
• This service can send SMS (also with Notification) to any number in the world at low cost.
• Scrapes a web page for its HTML code
• Instantly determines the validity of an email address or domain
• Determine the country that an IP address relates to
• Access World Time

Web Services List