I have some young seedlings that I started in Jiffy Pellets, and they are now ready to be potted up. I at one time had hundreds of these little pots, all sizes, but I gave them away. Now I sure wish I had just a few. Does anyone know where I can get some, either free or cheap or for trade.
Free or cheap may be a challenge at the beginning of the season. Maybe check your local Craig's list. Around here some of the independent garden centers (that grow their own) sell the 4, 3, & 2 inchers individually. And there's always eBay.
Know anyone who eats alot of yogurt? Even tin cans will work in a pinch. Or those heavy duty paper cups. For stuff with long tap roots I save & use half & half cartons. If you have curbside recycling you could go out on a night raid with a big shopping bag... you might find just the thing!
There are a ton of things around your house you can use to upgrade your seedling's living space...soda bottles, salad containers, and when you use those things, you throw out less garbage! Recycling at the easiest level! My co-workers always ask me why I never throw out my plastic bottles, I just cut the top off and add holes to the bottom and wa-la! Instant plant container! I even grew lettuce in my salad containers from fast food places.