There is a link to the McClellan Oscillator from StockCharts among the daily charts presented in the Chart Updates section on the sidebar to the left.
It is worth looking at more closely, as we are now at a key juncture according to several measures, and are obviously winding up for a sharp move.
The bias in the odds is to the downside, but a wise trader remains open to possibilities of a trend change here, as support is building around 800 on the SP. A breakdown could move quickly if optimism turns to ashes.