It is highly unlikely to find free crown codes for "Wizard 101" anywhere as of 2015. There are some promotional pages and YouTube users who occasionally offer codes to subscribers or people who comment, but there is no easy, reliable, legal way to get free codes without them being purchased by someone, so the best way to acquire codes is to buy them yourself.
Diligently watching and following some YouTube users or streamers known for giving away codes are the best hope of getting any crowns for free by honest means. Sites that offer free codes for nothing in return are scamming those who don't know better, stealing information or infecting innocent peoples' computers with malicious malware contained in downloads. Steer clear of anything that offers something of value completely free.
KingsIsle Entertainment makes its profit from selling crowns, so it is understandable why the company would like to prevent anyone from getting them for free. Due to the system in place, where the game is offered for free, it would be illegal to take money from the company that runs a game. This makes it highly unlikely that there are any legitimate and legal ways to acquire free crowns.