Bitcointalk is number one source to get almost everything. You can see bounties in the altcoins marketplace on the forum. There is risk in everything including participating in bounties. Not all projects are successful but who know. Aside bitcointalk, i will recommend bountysuite, bountyhive and bountyplatform. They are also good places to participate in bounties. Almost every bounty on these sites can also be found on bitcointalk.