Gamcore is a very popular place to play flash games directly in your browser.
They sort their games by date, best, popular, top rated and a lot more. Also you can just pick one out of more than 100 tags to find what you want.
When you select a games you will get one annoying popup, but afterwards you can play it for free and you are also able to comment the game.
Since it has quite an active community you can first check if the games is good or not.