Extracting POST params with Express.js 3

I'm just getting started with node and express.js and I'm having some trouble dealing with a POST request. I'm posting info that will be written to an activity log. The request looks like this:

POST /activities/log HTTP/1.1

san=3252080&event=MY_EVENT

My server (the relevant part):

var app    = express();
var routes = require( './routes' )( app );

app
  .use( express.bodyParser() )
  .listen( port );

My route:

activities.log = function( req, res, next ) {
  console.log( req.body.san );
};

The result (minus stack trace):

TypeError: Cannot read property 'san' of undefined

I'm sure I'm missing something simple & fundamental, but my code seems consistent with what I've seen in my searches so far. There are similar questions on SO, but none that match my scenario or give an answer that works for me.

var app    = express();
app.use( express.bodyParser() )

require( './routes' )( app );
app.listen( port );