For us Americans Wallstats has one of the most significant and suprisingly easily readable informative "posters" I've ever seen:
Death and Taxes (nonflash image version
Here). Linked because the real thing is 3500x2300 so a thumbnail would be useless.
It's a graphical representation of the yearly US discretionary budget arranged in a very self explanatory way. To get you started: Every circle is sized relative to the total discretionary budget, labelled in it's amount and percentage (red for expense, green for income), and the circle itself is a logo representing what the money is being spent.