How much money is being doled out in fees for every block right now?
There are some useful charts that show information about, amongst other things, fees per block.  Fees per block are currently trending downwards, but that is due to the additional hashing power coming on-line which means that blocks are being mined faster and so the average number of transactions (and hence fees) in an individual block is dropping.  Expect this to balance out sometime soon as the network takes account of the increased hashing power out there.

Right now, if you assume that transaction fees sit at around 0.25BTC per block you won't go far wrong.