I am not the best at organizing but I have found that there are some simple tricks that have helped me keep the chaos to a minimum.
The Car:
I have three kids and one on the way and have a Pathfinder. I have found that there is always something being left in the car or trash being thrown on the floor by someone at all times. It drives me nuts! So here is the system I came up with.
For diaper bags and necessities, I keep 2 or 3 diapers and a small bag of wipes in my glove box at all times. This enables me to take trips with my kids without carrying a bag every time. When I do need a diaper bag, such as for daycare, I have a row of hooks right inside the door from the garage. Every time I get out of the car, I grab the diaper bag and hang it on the hook on the way in. So instead of my car being the place to house the bag the hook is. The hook system is also used by everyone for coats and backpacks. Everyone is required to grab their own bag and hang it on the hook as they walk in, with the exception of the wee one of course.
For trash and such, I am not sure if all cars have this but I have a pocket in my door that I constantly put my trash in. It is easy to get to when I am driving, and easy to unload when I get out of the car. All I had to do is make it a habit to grab the trash when I get out and before I unlock the kids. I have my big trash can in the garage close to where I get out so it is an easy grab and dump. If I grab the trash each time it never gets out of control. I just make it a routine.
For all the extra stuff you need in your car - I keep a roadside assistance kit in the far back. I have a blanket back there when it is cold outside and reusable grocery bags. Outside of that, I haven't ever really traveled with a travel toilet, extra blankets or jackets unless I am going on a long trip somewhere. I am thinking you may just have a bit too much back there. It can get overwhelming.
To maintain it all - I do my best to make it a habit to remove extra stuff every time I get out of the car. If you make it routine (key is before you unbuckle kids) it is a lot easier and it never seems like a big job. I also make one day a week that I clear my purse and my car out. Even with a routine every day it is so easy to get junky anyways. It usually only takes about 15 minutes on a Friday to clear out the car and purse.
2. Craft Room - This is a hard one huh? I actually did a few cabinets. You can even use kitchen cabinets and put a top on them for work space. Then I simplify my organizing. For paper, I have one cabinet that each shelf is full of paper (laser paper, decorative paper, construction paper, card stock). It isn't necessarily perfect but I know all the paper is in there and I can shut the door so I don't see mess. I do this same concept for everything else, i.e., cutting supplies (scissors, die-cuts, etc.), glues or anything that makes things stick. etc. Then I don't freak out about everything being perfect in there I just make sure it is on the right shelf. The big part to me is to be able to shut doors and not see it all, otherwise I feel like it is a mess and not organized. I also use buckets when needed, like for my die-cuts, I have about 30 of them so I put them all in one plastic bucket on the cutting shelf. Make sense?
Office - This is a crazy place too! The BIGGEST thing here is to have a place for things that cannot be filed yet such as bills to pay, people to call, coupons to use this afternoon, etc. I have a stackable organizer on my desk that I put all that I need in it to be addressed. Here are the labels for the organizer - Bills to Pay, Calls, File, Coupons and Events, and To Do. I NEVER put my kids school stuff in there and NEVER let junk mail go into the house at all unless I am truly going to address it then it goes into my To Do or Call file. Then just like my car, I take 15 minutes one day a week to go through it and dump anything that is outdated or not needed anymore. For the record my File cubby is the worst, I always fall behind on that - YUCK!
Hope this helps, I just think the simpler the better then you don't have the overwhelmed feeling when you need something or have to address anything.
Good luck!