My SO and I have an excel spreadsheet in Dropbox. We enter expenses whenever we get back to a computer, almost always by the end of the day.
The spreadsheet has evolved to be pretty badass, including some fancy equations that automate some inputs. We can enter an expense in one place, and it will automatically show up in the subcategory column, which goes into the category total for the month, which is also shown in the Monthly Totals tab, where everything for the month is added up so I can see a total of what we've spent so far this month.
At the end/beginning of every month, I update some pretty column charts, so I can compare spending across the year. Recently I've added a nice pie chart of all the subcategories, which my SO even shared with the parents because it was so interesting.
Our categories and subcategories are:
-Food, ie groceries (subcategories: meat, stuff from the chain supermarket, fresh veggies from the local market, emergency lunches)
-Fun, ie everything (subcategories: eating out, booze [alcohol+coffees], events, clothes, grooming, gifts, etc)
-Transport (subcategories: car, petrol, bikes, public transit)
-Travel (subcategories: planes, ground transport, accommodation, food, activities)
-Needs (subcategories: rent, utilities, phones, medical expenses, etc)
We have a loose budget for the broad categories, which makes it easier to track, but if spending is high, we can pinpoint what tripped it.