What is the total number of Bitcoin transactions processed so far? Possible Duplicate:
  How many transactions have been included into the blockchain?  




The question explains itself.
You can chek this and other statistics in:
http://blockchain.info/

With the available data, the simplest way is taking the number of blocks:
http://blockchain.info/q/getblockcount
and the average number of transactions per block:
http://blockchain.info/q/avgtxnumber
and multiply them. As I'm writing I get 215749*238=51348262 transactions.

The daily number of transactions is also online:
http://blockchain.info/charts/n-transactions?showDataPoints=true&amp;timespan=&amp;show_header=true&amp;daysAverageString=1&amp;scale=0&amp;address=

You could write some code to count the transactions directly from you local copy of the blockchain, but if you want a fast figure the links I've written are enough.