One of the best things my girl and I did was write a story together.
I started the story, wrote a few paragraphs, then gave the disk to her. She read what I wrote then add her paragraph or two, then give it back to me to read and add on.
Before long it turned exteremly erotic and opened a whole world of hidden fantasies. Some we played out and others remain fantasies.
Very fun and couldn't wait to get the disk back!