Active Den

ActiveDen is an online market place for flash files. At ActiveDen you can buy and sell royalty-free Adobe Flash and Flex files for just a few dollars. Items are priced on the complexity, quality and use of the file. The site is home to a bustling community of Flash designers and developers and is the largest Flash library on the web.

Along with being able to buy stuff you are allowed to sell stuff.
It is very easy, just follow these steps

1. Become a Member – Become a member of any of the Envato Marketplaces.
2. Read the Authoring Tutorial – This is an overview of some important information you’ll need to know about uploading, copyright and selling.
3. Take the Author Quiz – The author quiz tests that you’ve understood the authoring tutorial. It’s a simple process to take and once passed you will be eligible to sell on the marketplace that you took the test on.
4. Select Exclusivity – Authors selling unique items on the Envato Marketplaces are eligible to receive between 40% and 70% of every sale depending on the sales volume. If you wish to sell the same items elsewhere then you receive a reduced 25% of each sale. Note that you can sell other items elsewhere as an exclusive author.
5. Begin Uploading – At this point you are now an author and can upload your content.
   

When your items sell you will be accumulating earnings which can be paid out in one of three ways:

• For earnings of less than $50, you can spend your cash on any of the Envato Marketplaces. If your balance is still below $50 after 12 months, you can withdraw the balance to a PayPal account.
• For earnings of more than $50, you can request a payout to a PayPal or Moneybookers account. Payments are processed at the end of each calendar month and paid out on the 15th of the following month.
• For earnings of more than $500, you can request a payout by bank cheque or wire transfer. Note that bank international cheque fees can be large.

Since ActiveDen is part of the Envato Marketplace, you are able to access the other online marketplaces with your one account.
There is http://audiojungle.net/, http://themeforest.net/, http://graphicriver.net/, and http://videohive.net/.

They also have sister sites for tutorials at http://tutsplus.com/. Most importantly they have a specific tut site for flash at http://active.tutsplus.com/.