Is it legal for teenagers to sell homemade crafts (not food) to people in Oregon US by knocking on doors to raise money for charity because they think it is fun and good experience?

Legal, possibly, advisable, not really.

What charity/charities?

Most people don't want peddlers knocking on their doors selling goods. Better to set up a booth at a craft fair.

Who would believe a teen ager selling homemade stuff door to door is doing it for charity?

Usually requires a license and a registration number to prove it is not for personal gain. Unless the person has this, then NO.

How old are the teens?

In many places local laws/regulations cover door-to-door sales.

Booths at flea markets, fairs, etc. would probably be safer. Though it may be more expensive to start, they would probably make more in the long run.

Selling to raise money for charity is a good idea, but the people who buy as a tax write-off will need more than a teen's say-so, so they need to find out what regulations there are for non-profit fund-raising. Plus contacting the charity/charities to make certain the organization(s) do not have regulations for fund-raisers to follow.

It looks like it could be a very good lesson in business for them if they are involved in the business aspect as well as the creative and selling parts.

Do they have a written agreement with the charity ? Or at least a verbal one. Also some larger cities have city laws. In Atlanta ( I know different state) the city has a law where any charity worker has to have a ID from the city and pay a bond. To get donations or do work asking for money publicly.

Is all the money going to charity, or just a percent?

And this is a business, so unless they are covered directly by the charity, who approves of this, they are operating a business, and will need a city business license in almost any location.

Want to add one other related story.

This is in Oregon, our church, while not selling anything, was getting donations and donations of food from various stores, and making sandwiches and meals for the homeless. Along with having some clothes, coats and blankets in the car.

The city where this was happening, said we had to have a license for the kitchen that prepared the food, be inspected by the health department, and have some other license because of the clothes and blankets. Of course the pastors home kitchen could not pass any health codes, so after about 1000 dollars in fines or penalties, the church stopped all work with the homeless from the cars.