My students don't start back to school until September 3 this year, but I already know what will be on their desks when they walk in the door. I have a page with a list of questions about their interests in and out of school. I use it to find out about them, but then I put in a time capsule for the last day of school.
If you would like a free copy of the Time Capsule page I use with my students, click here for the post on Artistry of Education.
Here's another tip: I use an empty oatmeal box with aluminum foil for the time capsule. It's the perfect size for the roll of papers I need to store for the school year.