GoToMeeting is a good video conferencing solution for large groups.
There are two plans for GoToMeeting - Professional and Business.
Professional is $12/month per organizer and supports up to 150 participants in a meeting. Business is $16/month per organizer, supporting up to 250 participants. With these types of accounts you are given unlimited meetings with no caps on meeting time, screen sharing or chat. All you have to do as the organizer is create the meeting and share the link to the members of your team that you want to be in the meeting. Because it's able to support large groups, it's great to create one account for your team and have users create meetings on that single account if at all possible, to avoid having to pay for a lot of different accounts.
I used GoToMeeting in the past with other organizations I worked with and had large meetings with over 100 participants and didn't experience any major issues with video or audio quality. As with any video conferencing software, there were occasional hick-ups, but I never experienced a dropped call.
Overall, I think GoToMeeting is great for large groups, because it has great pricing and features for both of the plans that they offer.
This user rated GoToMeeting's support for large groups: 4.0