Recently, I've seen bar or strip modeling showing up more and more in several different aspects of math. Bar modeling is often associated with Singapore math which uses it heavily in their program.
If you are not sure what it is, there is a lovely presentation that explains so much of it. This 52 slide presentation is mostly geared at elementary but it has some excellent videos embedded and provides some great examples.
The Pensive Sloth has a great example for using it with algebra. I wish I'd seen this earlier in the year with I introduced solving one step equations with my students but I do see a way I can use it with them and linear equations. I think it would be a wonderful way to reinforce solving equations while teaching about linear equations.
NCTM (National Council of Teachers of Mathamatics) has a great 6 page article on using visual tools in middle school. It has some great information and illustrations to help the teacher learn to use these modeling tools in class. The article is from the Oct 2015 issue of the middle school teaching magazine. I've got the issue at home so I'll go read it in detail to do some planning. I like that the author even shows ways of using visualization in several different ways.
Teacher Tube has a lovely video on dividing decimals which shows using the strip methods, fractions, basic math facts, and what to do if you don't remember the basic math facts. Its nice because of the first example where he shows how the drawing relates to the actual division problem.
This site defines what a tape model is, how it is used and provides suggestions for its use in upper elementary, middle school, and high school. It includes suggestions for implementing it, videos, and reminds teachers to make sure that the topic can be done via bar modeling. This article suggests it as method or differentiation with students who lack conceptual understanding.
There are several youtube videos that show how to use strip modeling to show how to solve simple equations etc but I have not been able to review them because my home internet is down and the one at work has blocked you tube.
I just wish there was more information available using it in middle school and high school because we all have students who need something like this to help them learn better.