The folks at Iraq Coalition Casualty Count track the number of dead bodies found on the streets of Baghdad every single day (as reported by the media). I tabulate their numbers, and I reported them most recently here (look at my third graph). The number of dead bodies found on the streets of Baghdad was 735 in January and 540 in June (a 27 percent drop).
If you want to check for yourself, go here to look at the daily casualty reports for January (by selecting January 07 from the drop down list at the top left of the screen) and then do the same for the daily casualty reports for June 07. Glance through the reports for stories like this from 1/27/07:
BAGHDAD – Police found 40 bodies, most tortured and shot dead, in various parts of Baghdad, a police source said. Two of the victims were women.
In January, there were seven days in which more than 40 bodies were found, and there was one day in which 60 were found (1/10/07). By contrast, in June, there was not a single day in which more than 40 bodies were found. This is not debatable. That story says:
During the month of June, 453 unidentified corpses, some bound, blindfolded, and bearing signs of torture, were found in Baghdad, according to morgue data provided by a Health Ministry official who spoke on condition of anonymity because he was not authorized to release the information.
The number of unidentified bodies found in Baghdad was significantly higher in June than in January, the month before the deployment of additional U.S. and Iraqi forces began in the capital. However, the overall number of civilians who died in violence in most Iraqi provinces has generally declined since January.
In January, 321 corpses were discovered in the capital, a total that fell steadily until April but then rose sharply over the last two months, the statistics show.
The June number is reasonably close to the figure you get from Iraq Coalition Casualty Count, but the January figure is way off. The numbers reported in the media (tracked by Iraq Coalition Casualty Count) are reliable. The Washington Post has this wrong.
Wixted addresses the Washington Post story at greater length here.