Augur is the only ICO I still hear a lot about in terms of having an actually useful purpose (beyond the market surrounding the coin itself). So this should be at least one correct answer to OP's question.
I've used it and it's fairly straight forward if you're tech savy. I bet on the midterm election, and the price of ETH. Since it's just a set of smart contracts, I expect market makers to start building 3rd party UI's to shill their markets, which should be interesting.
Disclaimer: Have never used it myself.