First, for organizing your scripts, I've always used a trapper keeper (mine zips shut) so that I can have one show (and all of its info), then a big dividing folder, then the next show, and just keep switching out scripts as time goes on. Once out of the trapper, a script goes into its own standard 3-ring binder.
That way, I ALWAYS have both current shows on me at all times and I never have to say, "Hang on, let me grab my OTHER script." All I have to do is flip behind the folder.
Last summer I worked as an ASM at a summer stock place (all musicals). Often, the cast was separated into two rehearsal spaces. The director would work on book scenes with some of the leads in one space, while the choreographer would work on major dance numbers in the other. Generally (because I was more familiar with dance and music than the SM) I would go into choreography rehearsals, and take notes on that rehearsal. By the nature of how our rehearsals worked, neither of us could ACTUALLY know/record all the blocking for any show. But between us, we had it all - so compiled, it all came together.
The other thing was that for every show, I tracked props, and the SM tracked furniture. Our theatre was in the round, so we had to track who used what, and where it came from (out of 4 aisles). By splitting this (and then communicating later) we covered everything.
On a side note, just remember that in Summer Stock, EVERYONE is stressed and EVERYONE is working super-fast. Do your best to keep the mood light. One of my personal philosophies is to know how everyone in the company displays/deals with their stress. Since it's inevitable that they will have it, and I want to dilute it as much as possible, I want to know each persons tell-tale signs, so that I can help them to the best of my ability (in the way that they need help). Do they just need to vent for a few minutes? I'll be an unbiased ear. Do they need a long walk to clear their thoughts? I'll do my best to get them one - or take one with them after rehearsal. Do they just need a drink? I'll buy them a beer after rehearsal.
One of the most genius things a director taught me was the use of an "Emergency Five." Sometimes, the stress just gets too much for someone, and even though it is not time for a break, they need to -- or they may explode. They just tell the SM or director "Emergency Five," step outside, and take a breather. Sometimes we all just need to get away. And in Summer Stock, 5 minutes is like a few hours in normal time. The Emergency Five does wonders.