When I was in college, I saw another classmate's calling script: she had her entire script in sheet protectors.
HOWEVER...
She had written her blocking notes on the script, and used post-its for the cues, then slid the script pages into the sheet protectors. It was the thickest script I'd ever seen (until I SM'd a workshop musical), and though I never asked, I believe her reasoning was that she didn't want her post-it cues to move/fall out.
I was blown away by the expense of all those sheet protectors, and the fact that she would have to keep pulling the pages out to write notes or move cues around. Personally, I felt it was a waste of money and personal time. I only use sheet protectors, like Maribeth, for commonly used items like show calendars, contact sheets and scene breakdowns - things I'm pulling out of my binder/tray constantly, since I want them to last.
For my script, I make my slip sheet (I'd actually never heard of this term before this thread - I just call it my blocking page) with the ground plan at the top and numbered lines underneath. I then photocopy the slip sheet to the backside of each script page (hear me out...), then reverse punch my script so that the text is on the left and the blocking is on the right. Then I make 50-100 extra one sided copies of the slip sheet, hole punch them and have them standing by. I use the numbered lines to correspond with the text as to where the blocking occurs, then put my cues on the left side of the text page. So, pretty similar to Maribeth, yet again.

If blocking changes too drastically (I've had directors want version A, B....G of a scene), I insert another slip sheet and paperclip it over the original. Same deal if a new page is issued, just insert the new page, clip it over the old one. It sounds nutty, but it works really well for me when workshopping shows. I never lose my old pages, and it's so easy to let the playwright or director know where things used to be when they get confused.
I do like the idea of the sheet protectors for line notes, but I would still prefer to do the short hand in my script to know what they missed and erase later, once again, like Maribeth.
It's good to know that I seem to know what I'm doing - since it's so similar to what others do.
Though lately, my calling scripts have been electronic - and sometimes I make a combo electronic script with blocking and cues (though mostly just for staged readings). When you have two scripts, there really isn't a worry of your blocking getting in the way of your cues.