Wonderful feeling isn't it? We too are debt free. Here's how we keep it that way.
Joint account for bills, personal accounts for treats, presents and personal items. Having money that is yours to spend as you like without jepordising family finances is empowering. Dh is a stay at home dad, so every couple of months I transfer some money into his account. It's his for beer, CD's, gigs, clothes, presents and general flittering away. There are no arguments about what he's spending because I don't monitor it. Equally what I spend my money on is my business.
Any spare money, tax rebates, bonuses, refunds, birthday cheques, child benefit, dividends etc go into a 60 day savings account. On top of this, every time our accounts go over a certain amount (in practise for us about a month's salary spare) we siphon it off into ISAs. The 60 day account is used for getting over humps in financial planning i.e. the month council tax, car tax water bill and dh's birthday all come due. We also fund holidays out of this account.
Credit cards are the devils plaything. If the head of Barclay's bank won't have one I think this is a pretty powerful message about just how much they cost. Same applies for store cards, though if you MUST have one, I like the icecube trick. If he insists on having these cards, it might be worth sitting down and working out, before you buy an item, how much it would cost in the end to buy it using different methods, cash, credit card, store card etc. Seeing the figures in front of you can be quite a shock. You will find it is cheaper to liberate money from your savings account, even accounting for no notice peanalties.
A tip from my FIL, put into a savings account what you WOULD have paid on the mortgage each month. Now personally, I think it should not be quite as much, otherwise, where's the fun of being mortgage free?