Create a poster-sized calendar numbered 1 to 30 one month before the beginning of summer vacation. Hang this in the room and attach 3-inch square sticky notes over each of the days with the corresponding number on the note's front. Write on the back of each note a prize that will be awarded to the student who pulls that sticky note from the calendar at the beginning of the school day. Starting with 30 school-days left until summer starts, choose a different student each day until all of the students have had the chance to pull off a note and get a reward. Use good behavior, highest test grades or displays of citizenship as reasons to select a student to remove a note. The rewards written on the back of the note could be a homework pass, a sticker or extra reading time. Put one or two classwide rewards such as extra recess or a class party on the last day of school.
Create a bulletin board in the classroom and have students bring in pictures showing their plans for summer vacation. Each day, a different student gets to put his picture onto the bulletin board and tells the class what he will be doing over the summer. For older children, have the students write essays that they will read on the day they put their picture onto the bulletin board. This is a reverse of the old "What I did on my summer vacation" paper. It can easily be tied into a grammar lesson on the future tense.
Instead of counting down the days remaining with numbers, use the alphabet. Have the class brainstorm ideas for themes for each day beginning with that letter. For instance, "A" could be "Animal Day," and the students could write a poem or paper about their favorite animal. Younger classes could have a short story read to them. Celebrate one of the theme days each school day, starting 26 school days before summer until the last day of school when the class reaches the letter Z. This could be "Zipper Day," when all the students wear clothes with zippers, "Zebra Day" with everyone wearing black and white, or "Zoo Day," and all of the students write about or draw their own imaginary zoo.
Take some time during the last days of school to create a classroom yearbook. Each student writes a paper about their favorite memories from the class and draws a self portrait. The teacher makes copies of these and puts them into a report cover or folder with brads for the classroom yearbook. The last day of school, the students can have each other sign their yearbooks.