Seems like I've been out for a bit. Reconfiguring the Physics curriculum in the transition to NGSS leads to occasional jags of spontaneous development. Not nearly as exciting as that makes it sound. But it keeps me off the blog nonetheless.
Here's something I developed for instruction after Newton's First Law/Inertia and before our full-on Newton's Second Law lab.
It's intended to scaffold some existing knowledge and suggest a = F/m. It uses PhET's "Forces and Motion Basics" sim (not to be confused with the "Forces and Motion" sim—that's a different sim).
Here's the sim:
Here's the sim's page at PhET.
And here's my lab: Pushing Things Around.
I hope to get it set into my own PhET Tech Labs page sometime soon. Patience!