Beware of "open data" cheerleaders. Several of these things are simply resume fodder -- the CIO announces this amazing API at a fancy conference, (living it up traveling on the taxpayer dime) and the open data people fawn all over them. Value/substance of the API? Zero.
I was excited to look at the USA Search API:<p><a href="http://search.usa.gov/api" rel="nofollow">http://search.usa.gov/api</a><p>I assumed it would have census data, etc. But disappointed to find out it only has one api: product recalls.
This is a nice listing to explore but I have to object to the OP's optimistic tone of "the government is listening to us, so let's make some apps"<p>Look deeper and you'll see that many of these APIs are junk, particularly the crime reports (week-period aggregates are useless). The reason why developers don't make apps is because the data is incomplete and non-normalized and redacted in unknown ways. Making apps out of the data is a poor use of time and helps to obscure the failure of government to modernize their data collection and publishing systems.