I haven't heard much of my department either. I've sent a couple of emails to the secretary, and my adviser but haven't received anything yet. I only managed to register to a couple of classes from remembering what they said during the interview day and finding the study plan online in the departments website.
I wanted to relax this summer too, but I caved in and got into a paid internship running from mid-June to early-August (16 hours a day/7 days a week, few "rest" days in between internship duties). Hopefully I am not too burnt out, but I actually have been having a hard time coping since graduating this past December and not getting any type of pay (since I am currently an unpaid intern/volunteer in two research labs). I also need the money for the first two months of rent since my assistantship is set up in a biweekly paying method and won't see any kind of money until probably mid September.