Digital BW, The Print

Can someone post or direct me (WWW) to a resolution chart for 
printing?  What I want to know is what image resolutions and DPI are 
best for each sized print, 4X6, 5X7, 8X10, 11X14 and so on.  I know 
that there is a point in which everything else is overkill for a 
specific resolution and DPI. 

Thanks in advance,
Duncan