Microsoft has some great planning worksheets for SharePoint 2010 @
Planning worksheets for SharePoint Foundation 2010
Planning worksheets for SharePoint Server 2010
I found that I really needed one for Service Applications and one for Service accounts as well and thought I would share my efforts. As with most of my stuff it tends to favor function over form but hopefully some will find them useful.
SP2010 Farm Configuration WorkSheet
SP2010 Service Accounts WorkSheet
SP2010 Service Applications WorkSheet