I was wondering if anyone has used math journals/Notebooks in their classroom, and if so if you have any thoughts on how to make it successful? I have used them with my science class but this will be my first time to use them in my math classroom.

I have used math notebooks with my 3rd graders. In the back, they glue in any reference pages that I give them, as well as math vocabulary. The actual journal entries are usually a reflection. I post questions such as "What strategies worked for you?" "If you had to explain this center to someone, what would you say?" "What was hard about this activity?" "What was easy about this activity?" "What connections can you make to other work we have done?" "What are still wondering about?" "What sense did you make of our work today?" Sometimes their thinking is recorded in sketches/diagrams/drawings depending on the task. Occasionally we also record problems from the textbook in our notebooks. They also use the notebooks to prove their answers, explaining their thinking.

They write their individual reflections, then we meet on the carpet and they share their reflections in pairs and/or with the whole group. We record their thinking on chart paper.

I have found the notebooks to be very helpful in getting students to think about their work. Our whole group discussion is much richer as well. I do not grade everything in the notebook, but I do some quick checks once in awhile. For my struggling students, the notebooks give me a picture of where their misconceptions are.

I've been using them for a couple of years with third graders, too, tweaking them each year (like everything else!)
Here are a couple of quick thoughts:
It's important for kids to understand what reflective thinking means, so you need to model that. Same thing for "show your thinking."
Show kids how to put an entry in the notebook. I have kids include a title and the date. Sometimes I'll have the question typed and cut, and kids put that into their notebooks before they start their enty. Depending on the age, you may need to show them how to glue an entry into the notebook!
Develop a rubric with your student, and glue that into your notebook, too.
Sometimes I'll have kids work on open-ended problems, and sometimes I'll have a more general question. If it's the start to a unit, it might be something along the lines of "What do I think I know about multiplication?", etc. Our first entry will be something along the lines of "what do you like about math", "what is challenging for you about math", and "if you were the math teacher, how would you work with students." It's pretty interesting to read what kids think.
Like the PP, I don't grade the journal- but I do check for misconceptions!

I am moving up to sixth grade this year after spending most of my career in either 3rd or 4th. With Common Core on it's way, and with my new school's emphasis on deeper thinking and reflection, I think using a Math Journal is a great idea. I haven't used journals outside of indepent reading, but I think it's a great opportunity to incorporate it into Math. We are a new Charter school, (part of a large, multi-state company) so i will be teaching Math and Science this year.

I am bringing my class up to 3rd grade this year. We used a math journal last year, but I am looking to expand on it this year. My bonus is that they are already "trained" on how to use it and now I can just add to that. My students had reflections in there, as well as how they tried to solve more difficult problems. I agree with the others when they say it is a great resource to see a child's thought process.

I have been reading about Interactive Math Notebooks on Pinterest. Like a PP, due to CCS, I am implementing notebooks this year for my 6th graders. I am SO excited! In OK, we don't start CCS for 2 more years, so I am going to do some this year, and some next to be ready for the following year and CCS. I am going to CONCENTRATE on using the notebook for note taking, defs, examples, etc. this year. I realize that is not the interactive part, but I want to make sure I don't bite off more than I can chew. Then, next year, i will begin the reflections and proving.

I have used math journals in 2nd grade. I would give them a problem and they would have to solve and explain how they came to the answer.

I have also talked with other teachers at my school about using math journals again this year. They said, they have used a journal prompt that they have the students glue in their journals and then write how they will go about solving the problem.

I'm using math journals with my 8th grade Algebra I and Pre-Algebra students. The notebooks stay in crates in the front of the classroom, sorted by section. When they come in, they grab their notebook before sitting down and complete the bell ringer in their journals. We discuss them, and then they pass the journals back up. I had them number all f the pages in their journals before turning them in, so Bell Ringer 1 goes on page 1, Bell Ringer 2 on page 2, etc. I use both example problems and reflective writing as bell ringers.