The following Microsoft SQL Server T- SQL query will list unique indexes which are not primary keys:

USE DatabaseX

SELECT IndexName = Name,

       [Table] = object_name(id)

FROM   sysindexes

WHERE  status & 2 = 2

       AND ID NOT IN (SELECT parent_obj

                      FROM   sysobjects

                      WHERE  xtype = 'PK')

       AND ID IN (SELECT id

                  FROM   sysobjects

                  WHERE  xtype = 'U')

Related articles:

Unique Constraints and Unique Indexes

http://www.sqlusa.com/bestpractices2008/allindexes/