Rush seats vary because they are for most empty seats at the show. Next to Normal has a general rush which is for the first row and then the side boxes, but be prepared to get to the theater at 4 a.m. for the box office to open 6 HOURS later.
just giving my opinion/warning on Next to Normal...the box seat I got was terrible. I rushed back on Aug 17, got there at 5:15, and was 9th in line, and got a right box seat. From there, I missed all of Jennifer Damiano's piano playing/her scenes with Henry there, as well as all scenes extreme downstage left (like when Diana brings out the cake...could'nt see anything). Also, for a bit of Act I, everyone in our box had to lean over the side to see what was happening downstage left.
I was lucky enough to move to a front mezz seat, though, and had a fantastic view. Next to Normal's last row (row H in the Mezz) is only $36.50, and I would definitely go with those if you can't get to the theatre at 4am.