Ever since I was a kid and all of summer was a vacation, I've always visualized the summer timeline as a single linear strip. In 1999, using Adobe Illustrator, I designed such a calendar, 4 feet long from June through August. (Parts of May and September can be added if desired.)
Here's a fuzzy idea of what the calendar looks like:
The printout has a strip for each month. You cut out the strips and tape them together (on the back). Here's a low-resolution image of the sheet you print out and then cut up into strips (2007 version):
The calendar is designed to print on 17" paper (Tabloid size or A3). You can scale it down, but then the boxes get quite small.
Download summer-calendar.pdf to print the 2007 calendar.
If you have Adobe Illustrator, you can edit the PDF file to adapt the calendar for any year by making the approriate layer visible; there is a layer provided for each of the 7 possible calendars.