There’s a “beta” release of an LDAP claim provider for SharePoint 2010 available on CodePlex now. I believe the SharePoint product group created this and released it. It will allow the people picker to search and resolve AD users when using claims. Check out the release on CodePlex for more information. http://ldapcp.codeplex.com/ Check out the description from the site.
“OOB SharePoint 2010 does not try to resolve the values that users type in the people picker when the web application is configured with a 3rd party STS (SAML mode) such as ADFS. This claim provider adds support for search and resolution against Active Directory when a user types a value in the people picker.”