Confession time: I do a bad job of letting my older students have independent reading time, so the last couple of weeks, I decided to remedy that issue and they enjoyed the special privilege of just being able to read.
3rd-5th grade: they rotated between draw your own comic strip, typing practice, make a secret code, post-it bingo with summer related words, and read a magazine under a table "tent"--library has round tables that seat 4, so they make for decent under table reading.
The last week I kept it simple: two tables at a time rotated between last days of school educational websites (many of them choose typing practice still), read a NookColor at your table, or read a magazine under a table "tent".
5th grade got an extra special last week of school. They switched between typing/educational websites and "Minute to Win It" games.
For my younger students, I discovered that it is easier to put centers material in storage bins (from the dollar section of Target) the size of magazine holders, so that the students stay at their table and the centers come to them. It is a great little management technique.
K-1st: centers included environmental print puzzles (or the front side of food boxes cut into squares), sponge blocks (cut the size of Jenga pieces), My First Hidden Pictures with dry erase markers (I remove the two page spread from Highlights High Five, tape it together, and have it laminated), grab a book and read it under a table, and a peek-a-book.
My 2nd graders this year were a bit of a challenge because they like worksheet work and I'm not used to being a worksheet teacher. Their last two weeks of school consisted of book series parties, Elephant and Piggie by Mo Willems and Pete the Cat by Eric Litwin. I printed off some of the publisher provided event activity sheets for Elephant and Piggie and made each sheet a center, plus I provided a stack of the books for students to read. They LOVE hidden pictures, so their centers included a hidden pictures sheet. For Pete the Cat, I found a how to draw Pete the Cat, a Pete the Cat word search, read Pete the Cat books, and explore last day of school websites.
I will continue to run the last weeks of school this way in the future.