We get hideous amounts of junk mail (granted, most of it is shiny horrible catalogues which you shouldn't use) but there's always a 'newspaper' or news-like catalouge, which are just fine.
You can make little seedling pots out of sheets of newspapers, and then just plant the whole thing right in the ground! It biodegrades quickly and the plants grows up happily. The same thing can be done with toilet rolls which are plentiful. Everyone uses toilet paper.
With the toilet roll pots, I bent over the edges at the bottom to make it a smaller hole, and put in some kitty litter (we put used stuff under the stairs/in garden. It's compostable) for drianage at the bottom before putting in potting mix. Plant you seedling and away you go!
In there is also an empty (washed) container of nuttelex margarine. We may as well use them too...I pounched about 5 holes in the bottom with scissors for drainage. Drainage is very important.
And to think I was thinking about buying up some plastic seedling tubes! Shocker. Ha.
Anyway, the above picture are my cpasicum seedlings that I've pricked out so far. The toilet rolls are in the tupperware container to help them stay upright. I intend on filling up the window box tray with the newspaper pots (also to help them stand up).
The only disadvantage that matters is that you can't just leave it out in the rain...they'd disintegrate way too quickly. So I've just put them under the eaves where the rain doesn't fall, and then I can control the water that goes on them :)
I'm surprised I got such a good success rate with my capsicum seeds, especially considering it was just a regular conventional supermarket capsicum. Hopefully some of them continue on their merry way.