Upgrading SMS 2003 sp2 to SQL 2005
Brian Mason has a great checklist available in the forums if you are tasked with doing this.
http://www.myitforum.com/forums/m_129606/mpage_1/key_sql%252C2005%252Cchecklist/tm.htm#155415
Thanks to John Nelson for bringing this to my attention by posting it to the SMS/ConfigMgr email discussion list.
Jeff Gilbert also has some great info on his myITforum.com blog:
Upgrading SQL for SMS Sites