Situation: You have a lot of groups as groupOfNames in you ldap directory. How to find all such groups a known member belongs to?

The goupOfNames object might look similiar to this:
dn: cn=TestGroup, o=TestOne, dc=rekk, dc=de
objectClass: dcObject
objectClass: groupOfNames
cn: cn=TestGroup
dc: dc=TestGroup
description: Some test group
member: uid=00001
member: uid=00011
member: uid=schwarz,dc=Test DC,dc=rekk,dc=de

The query would be for uid=schwarz:
(member=uid=schwarz,dc=Test DC,dc=rekk,dc=de)

or more specific:
(&(objectclass=groupofnames)(member=uid=schwarz,dc=Test DC,dc=rekk,dc=de)

Also see LDAP Query Adventures.