For both WSS and MOSS I like to use the least privileged account methodology for all my deployments. This is considered Microsoft best Practice.
|SP_Admin||SharePoint set up account, used to install SharePoint. Local administrator on web front end. DB Creator on SQL.|
|SP_Farm||SharePoint Farm service account. DB Creator and Security Admin on SQL. Also used as the Central Admin application pool identity.|
|SP_WssSearch||WSS search Account.|
|SP_MossSearch||MOSS Search service Account.|
|SP_Content||SharePoint Content Crawl Account.|
|SP_Profile||User profile import account.|
|SP_SSPAppPool||Application pool identity for Shared Services Provider|
|SP_PortalAppPool||Application pool identity for Portal web application.|
|SP_MyAppPool||Application pool identity for Mysites web application.|
|SP_Excel||Excel Services service account.|
|SP_SSO||Single Sign On service account.|
Above is a general guide of what I use when deploying WSS and MOSS environments. Some of the above accounts are not needed for WSS.