Our house has many big windows and I'm simply too cheap to buy that much window blinds :P
I came up with this inexpensive, easy and yet decorative window blind.
It takes about 30 minutes to make one.
Step 1: Materials
a big sheet of cardboard (the one i used was kind of sloppy and had a lot of holes in it - you may choose a nicer one)
a long straight piece of lumber or anything else - it has to be straight thats all, you'll only need it as help for cutting)
a knive or cutter
2 hairclips or clothespins
2 hooks or heavy stones
1 big needle for the twine (works without but it'll much easier with the needle)