I've been asked lately what accounts I generally use for setting up SharePoint enterprise server farms.
This is always a hot topic and everyone has their own conventions and thoughts on the matter.

First and foremost, consult the guidance available at http://technet.microsoft.com/en-us/library/cc263445.aspx for your specific configuration.

That being said, here is what I normally do for 5-6 server setups (WFE/APP & Index/SQL):

DOMAIN\MOSSSQLSVC (SQL Service Account)
DOMAIN\MOSSSETUP (Setup Account)
DOMAIN\MOSSSRVFARM (Server Farm Account)
DOMAIN\MOSSWEBAPP0 (Generic App Pool Identity, add additional accounts as needed... )
DOMAIN\MOSSCAAPPPOOL (Central Admin App Pool)
DOMAIN\MOSSSSPAPPPOOL (SSP App Pool)
DOMAIN\MOSSSSPSVC (SSP Service Account)
DOMAIN\MOSSSRCHCA (External or special Content Access)
DOMAIN\MOSSSRCHSVC (Search Service)
DOMAIN\MOSSSRCHSVCCA (Search Service Content Access)
DOMAIN\WSSSRCHSVC (WSS Search Service)
DOMAIN\WSSSRCHSVCCA (WSS Search Service Content Access)
DOMAIN\MOSSLDAPSVC (Profile Import Account)
DOMAIN\MOSSEXCELSVC (Excel Services)

There you have it.. 14 accounts! Usually all set to some sort of enormously cryptic strong passwords I always forget.  If your not using excel services or crawling external content, you can usually thin it down 2 accounts.