The Internet has become the main place for advertising international opportunities, something we are all after. There is a plethora of websites, but not all of them are good. Some are outdated, some confusing, and some don't give out all the information. This is why I've decided to assemble a list of my personal favorites, and I expect you to comment yours in the comment section below! 
MUNPlanet, https://www.munplanet.com/topics/youth-opportunities?suggest=Youth%20Opportunities
For me, MP is the first on the list because there is no other website out there that so clearly and comprehensively shows the opportunities, whether it be international events, jobs, or conferences. Deadlines, application requirements, everything is very easy to find. Another gigantic advantage it has over other websites is its calendars, as well as the List of Fully Funded Opportunities. Surprisingly, nowhere around the internet is there a list of these, let alone for free. In addition to all this, this is a community which means that there will always be someone to offer support, advice or anything else you might need in trying to improve yourself by grabbing as many opportunities as you can.
Opportunity Desk http://opportunitydesk.org/?v=1
This website is one of the most frequently updated, and therefore most popular opportunity websites out there. It is also very clear, and what you're looking for is pretty easy to find. Overall, a very good online portal.
YouthOP https://www.youthop.com/
YouthOP is another great website where you can find opportunities. What makes them stand out among other portals of this kind is their search filters which enable you to search for what you need in a short time.
Opportunities for Africans https://www.opportunitiesforafricans.com/
This a great, comprehensive website. However, it is geo-specific and only features opportunities for Africans. If you live in Africa though, I highly recommend this website.
You're good to go! Be sure to add websites in the comments if you think I missed any.