Best site for custom fantasy football league?

My 12 team fantasy football league has been using Yahoo for years, but we are now looking to use another website. We want a website that allows for full customization of scoring, %of teams to veto a trade, the ability to trade future draft picks, ect. This is not a dynasty league but we do have keepers and would like to implement new changes to our league that Yahoo simply can not meet. What other websites are out there?