Application Grave Robbing ...
Need an idea for an application to design? Here's a list of projects that Google has abandoned over the years:
Some people see this list as depressing. I agree, to some extent. I was a real fan of Google Reader, for example. You also can go down the rabbit hole of conspiracy with Google Reader. Instead of picking the exact feed providers and reading them in chronological order, we now have a bunch of algorithms.
But the truth is, the list of projects killed by Google is really an opportunity. They saw something. They moved on. Keeping them going did not fit into their business model, but that doesn't mean they're unprofitable models.

The less popular 8.8.4.4 is slated for discontinuation.
Also, someone who resurrects a project that Google previously killed indicates to me these app developers are probably not going to just try to build the application in the hopes that Google will buy them. So it might result in more quality apps, not just a cash grab.
I was a big fan of google reader, too. Fortunately for me, theoldreader.com does a decent job of replicating the look & feel.