Everyone will say their personal favourite ones. Do your own research and look at the projects, are they solid ones? Look at the team: do they have experience? I would like to propose you the platform I am participating in right now: Crowdholding: https://www.crowdholding.com/
Although their ICO is still ongoing you can earn tokens by participating in the platform. All you have to do is log-in and leave your ideas and comments for co-creating. I wish you good luck and do not invest more than you can lose!