I personally use Excel, and for anyone interested, my financial records are structured roughly as follows:
The main sheet contains a breakdown (monthly) of my income (in my case, separated into salary, dividend, and property rental income received) and my expenditure. For fixed costs expenses such as mortgage costs, insurance, utility payments, taxes, credit card minimum payments (0% balance transfers used to buy assets), etc I put in exact figures and revise them if the bills come in differently (and if massively differently then question why!).
I don't micro-manage my expenditure and instead have a lined called 'expenses'. This is a set amount each month that I arrived at through trial and error based on my comfort level and realistically looking at what I may need to spend money on. This expenses line covers my food, train travel, entertainment and shopping - clothes, electronics, books, trips, dining out, etc. Each day money from this line is automatically deducted by an Excel formula and added to a lined called 'expenses already paid'. This way I can keep track of (up to) how much I am allowed to have spent already which tells me quickly whether or not I am on track.
Next to all of the income/expenditure data, I have a list of all my assets (property, shares, bank balances, cash owed, etc). Once a week I updated balances from here, and calculate a predicted balance based on where these are at vs which incomes and expenditures have already come in or paid out.
This means that I can very quickly see if I am overspending or not. If I am overspending then I pull in the reigns, live simply and slow down or stop any discretionary spending. From this I can also quickly see my net worth, and because I have previous data, I can track the increase of my net worth each month. This can be very motivational, especially in some month when I work hard, and spend little - several months last year my savings rate reached 70% (although I average between 50-60%). If in a slow month this starts to drop it's gives me a boost to go and seek more work.
At the end of the month, I reconcile my accounts, take a snapshot of all of this and place it in an archive (income/expenditure as well as assets/liabilities), and then start afresh with the new month. I have data for this going back to around 2006, when I first started budgeting (why oh why I didn't start this before the age of 25 I have no idea!). It's become such a habit now that I automatically do it every week.
I have also predicted my budget several months in advance, which is helpful as it also shows me the minimum I need to earn to keep the wolf away from the door. Luckily as I get older this amount is becoming less and less (more passive income, more earnings and more efficient at controlling expenses).
The other main pages of my spreadsheet include a detailed monitor of all of the credit cards. This shows me when their 0% balance transfer rates are up and calculates roughly the minimum payments, balances, interest rates and interest costs. This is very handy if like me you make use of cheap borrowing to fund asset purchases (I have about 15 different credit card accounts to manage so keeping them organised is a must).
I also have other sheets showing me whether or not a property deal is cashflow positive, compound interest calculators, and various simulators, all to help me make sound financial decisions.
So, all in all I prefer using my own Excel sheets to some other online system. This is because I've found most of the online systems seem to cater for average people who lock their money away in pensions and want to micromanage to the nth degree each little expense. I personally find looking at the bigger picture is more helpful in financial planning. Of course, getting cashflow positive each month such that savings and investments always grow is the first step and for that you do need to micro manage until you are disciplined. What I've personally found is that once I was disciplined I no longer found it constructive to micro manage each expense. Too much effort for too little gain.
So, I'm interested to read more about how other people do this, and if anyone is interested in my setup or has questions about it I'd be happy to share more!