Papageno, I know it sounds boring, but get a small filing folder. You can find them at Staples, or Walmart, or a million other places. Go to the office section. One of the accordian types or hard sided bucket types that have separated folders built in. They will usually come with folders but you may have to buy some. That will take care of any and all paperwork. Make sure to categorize it a bit or it will just be a mess of papers. Thing like “Receipts”, “Invoices”, “Medical”, “Insurance”, “Financials”, etc. Something like this, your tastes may vary for the exact style:

As for all around clutter, become a fan of bins. Get some cube shelves/storage at Target or Walmart or whatever is cheap around you. Right next to them will be bins that fit in them. Like this:

Throw all your crap in the bins, again hopefully sorted a bit somehow. It will get everything off the floor/counters/sofa and make the place look organized.
I personally can’t stand clutter and have always been organized like this, so it comes naturally to me. But recently this bin/storage cube trend has become popular and it’s really taken off and considered semi-trendy now. You can also get all kinds of baskets, bins and chests to store other things. The modular nature of them makes them all match and look like it’s thought out and part of the design of your home plus it takes up way less room than having everything strewn about.
To give you an example, one of those bins may hold all of my videogame controllers. Another may hold cleaning products. Another may have my binoculars and cameras, another full of bags of cords, adapters, etc. I’ve actually incorporated these cubes into my closets now to divide the shelves and give me a really nice looking, organized linen closet. Towels go in one cube, washcloths another, etc. The top of the cube serves as another built in shelf. The other advantage of bins is that it takes next to no time just to toss something in a basket or a bin, and makes looking for stuff easier as well. As I tell my wife: Bins! Bins! Bins!
I could go on and on about organization but to me it’s the difference between being a kid and an adult. When I see people’s house strewn about with crap I lose a little respect for them and see them as disorganized and a little off. If you are in the dating scene at all I guarantee women will look favorably on an organized house as well. You don’t have to be anal about it, but it really does make you look and feel more adult to be organized. I can’t stand clutter.
My two cents, YMMV, etc. But to me, an organized home is an organized mind.