There are three different ways to offer OpenIDs, each varying in complexity.
One approach is to outsource account management and security to a third party. For many companies, this approach may be quicker, simpler, and more cost effective. One current provider of outsourced solutions is JanRain‘s Federate, a software as a service (SaaS) OpenID provisioning and single sign-on solution.
Should you choose to host a solution yourself, you can avail yourself of one of the existing libraries, plugins or software packages that feature OpenID providing capabilities out of the box.
Lastly, and most challenging, is implementing custom support for OpenID in your software and account management tools. While this approach of course affords the greatest degree of control over the user experience, it is also the most risky and only for developers experienced with web security. Start by reviewing the specs and documentation.