The Rev. Dr. Safiyah Fosua, the Director of Preaching for the Discipleship Minstries Division of GBOD and the NYAC's 2009 Annual Conference Bible Study leader, offers some resource suggestions for Kwanzaa in her December newsletter which may be helpful in planning a worship service.
Below are the links and comments from Rev. Dr. Fosua's newsletter.
http://www.gbod.org/Worship/default.asp?loc_id=733,1151,1172&act=nav_loc
There are also a number of fine cultural and worship resources on the African American Lectionary site
http://www.theafricanamericanlectionary.org/PopupCulturalAid.asp?LRID=122 (Maulana Karenaga)
http://www.theafricanamericanlectionary.org/PopupCulturalAid.asp?LRID=60 (Bernice Johnson Reagon)