Let's say you've got family all over the country (or the world), and you're looking for a central, affordable spot for everyone to meet up for vacation. That can take quite a bit of research, but trip planner Seeusoon makes it a lot easier.
From the website, you simply enter a departure city for everyone in your group, then enter your travel dates, and Seeusoon will find the cheapest travel option for everyone. First, you'll see how much it costs (per person, on average) to fly to each origin city. This is helpful if you're trying to decide who's hosting Thanksgiving, for example. You can easily see which origin city is the most cost effective for everyone in your group.
You'll get other destination options, too. The site suggests the cheapest meetup cities around the world for everyone, based on the average cost of flight and lodging. Lodging is based on Airbnb rates, and flight prices are based on the cheapest deals their algorithm finds by searching hundreds of airlines around the world. Once you click on a destination city, you'll see a list of flight and Airbnb options.
The site's founders actually launched it originally with long distance relationships in mind, and it's great for that, but it's also useful for any kind of travel that involves multiple origin cities. It's an easy enough tool to use, and you can check it out at the link below.