There are several options for websites looking to allow users to sign in with OpenID. You may use one of the open source libraries available in many languages. There are also plugins available for several different content management systems and web-based services. Or you may use a third-party solution.
There are many libraries available to help you add OpenIDs to your website. Find a detailed list of these OpenID libraries here.
If you use a Content Management System (CMS) or a web-based framework or service for blogging, wikis or forums/bulletin boards, you can use one of several free plug-ins to accept OpenIDs:
Click here for more details about each plugin as well as a list of other web-based services with native support for OpenID.
There are also hosted solutions available from vendors that allow you to easily accept OpenIDs on your site: