Killed by Google is the open source list of dead Google products, services, and devices. It serves as a tribute and memorial of beloved services and products killed by Google.
XMPP based chat; being able to chat with anyone without them having to create a new account was wonderful.
Picasa; my wife absolutely loved it.
I loved the original Grand Central, better than Google Voice. I rarely use it, but every so often I have to give a phone number to someone and am not sure if I want them to have my real number. Now websites and companies reject the number, so not sure how much longer I will maintain it.
Picasa was a Windows application that you could use to organize your photos and do some editing. You could then upload to Picasa web host. It wasn't perfect but was great for free