GAfR. Same tools as Business and Education use I guess, but applied to my long distance relationship.
Hangouts for face to face time. Seeing each other's faces is critical. The most important piece.
Drive for project and organization. We're looking for a house, so I have a folder for that project. Inside is a master document with all the houses I've looked at, my review and their prices. In that folder are collections pictures I take of the houses with the address. These could be moved to G+ albums, but it's easier to have them all in one spot for right now, they'll also be deleted once we settle on a house.
Calendar since we're in different time zone it's difficult to stay organized and keep track of each other. I keep all my major events on their for the wife so she knows when to reach me.
Youtube. I recorded a video for Valentine's day. The video editor leaves something to be desired but I'm still thankful for Youtube's existence.
Android, while it isn't part of Google Apps, is an amazing way for us to connect. We play Words with Friends. We are able to send pictures of our day to each other, we have unlimited texts and take advantage of it.