For new bounty i think you can check new ANN thread.This way you can find newest bounty.You can check also bounties (altcoins) section.You can follow bitcointalk user's signature.You can follow this side.
https://icodrops.com/bounty-list/this website is really very good and certainly can help bounty participants to choose the new bounty. But it would be great if we ask first on their official telegram about the bounty that we will follow.