Ones that end in 0 or 5:

July 22 - 225th birthday of Friedrich Bessel, the first man to figure out
the true distance to another star using parallax.

July 23 - Tenth anniversary of the deployment of the Chandra X-ray
observatory.

And I missed this one from July 9, the thirtieth anniversary of the flyby
of the Voyager 2 probe past Jupiter, where the first really close-up
images of the intriguing Galilean moon Europa were taken. This event
was covered in one of Carl Sagan's Cosmos episodes, where he showed
images of Europa that had just been sent from the Jupiter system by
Voyager 2 in July of 1979.

And for those of you living in southeast Asia, there will be a total solar
eclipse on July 22. Thanks to modern technology, the rest of us will be
able to see it on the Web.

Details are here:

http://eclipse.gsfc.nasa.gov/SEmono/TSE2009/TSE2009.html

Did I miss any?