I like to use the envelope system for budgeting, but I can't escape the convenience of debit cards, so a few months ago I set up 5 debit cards, one for my primary account, food, gasoline, household items and personal entertainment. That way I can make an automated transfer from the primary accounts to the other accounts, and always know how much money I have left in each account.
But it is annoying carrying around 5 debit cards. I've heard that some banks offer checking or savings accounts with "sub-accounts" which you can create, simply for the purpose of logically grouping transactions. Anybody heard of this or have any recommendations?