Does uPortal support LDAP?

Yes, thoroughly.

uPortal integrates well with LDAP, able to rely upon LDAP for authentication, for user attributes, and for group memberships (but requiring LDAP for none of these and allowing you to mix and match your sources of authentication, user attribute, and group information).

A free and open source search portlet available from Jasig implements directory search against LDAP.

See also the uPortal FAQ, which has several entries related to LDAP, and the uPortal 3.2 manual, which has several LDAP-relevant sections, linked above.