The UN Youth Diplomacy Competition is an online Model UN competition for teams of up to 4 students. If your Impact Project involves politics or global issues it might fit in well! There are cool prizes too.
Registration for round 1 closes next Wednesday though registrations will remain open throughout the year. The time commitment is anything from a couple of hours per week to up to 8 hours spread across your team, so doesn't *have* to be part of an Impact Project, anyone interested is welcome to take part.
See http://diplomacy.unyouth.org.nz/ for more information :-)