Heard good of bountyportals.com. Never tried it in action but looks good. Check it out. You can participate in some exactly from there.
ive already have an account on this site and this site is run by a reputable member here in bitcointalk named ifran park. bountyportals.com caters a whole variety of bounty campaigns that mostly link on bitcointalk.org however bountyportals lately has been attacked by spammers , posting off topic and nonsense mostly medical stuffs. I dont know really know the primary reason on why someone needs to do it, maybe they are just jelous to the site itself?