Ian McDonald of Florida State University has calculated that the Deepwater Horizon oil spill‘s flow is approximately 26,500 barrels per day.  Here’s a report from the SkyTruth blog (http://www.skytruth.org/):

Deepwater Horizon spill estimates derived from USCG fly-over data (28 April 2010)

Figure 1. US Coast Guard map showing size and appearance of oil slick on April 28, 2010.

Figure 2. Chart of oil thickness and appearance.

A human hair is approximately 100 µm (microns). The main slick, which corresponds to the cross-hatched area was assigned a low value of 0.5 µm. We calculate a total volume of oil for this slick as 8.94 million gallons (212,000 barrels) (Figure 3). Considering that the oil in the water on April 28 has been deposited since the blowout and explosion on April 20, the flow rate should be on the order of 26,500 barrels per day. Some fraction of the total oil released will have been evaporated or emulsified and sunk in the time since the spill began, or collected by the response crews, so this should be considered a minimum estimate.

Figure 3. Volume of oil based on Coast Guard map (Figure 1) and thickness (Figure 2).