While many to-do lists (like "things to pick up at the drug store") are best left private, lots of lists are more useful when others can chime in and suggest things you might like. For example, Arin Sarkissian created a to-do list inside his new app Well where users can suggest new features for him to add. On the surface Well is a to-do list app on iPhone and web, but when you dig deeper, it's a community built around things you want to do. Since everyone can see each other's goals, it's simple to make comments on them or suggest new ones.

"The initial idea came to me when I was head of infrastructure at Digg," Sarkissian says. "I realized that I always knew what my coworkers wanted to do since I talked to them all day, but I didn't know my best friends' intentions." So he decided to build a tool to hold all the things you want to eat, or see, or watch, or do. Well is category-agnostic, unlike apps like Foursquare that only hold places you want to go. Each list you create (like "video games to play") contains everything you want to do, as well as things you've already done. Since to-do lists you create are public, Well offers an equally compelling reason to check what someone wants to do, as well as what they've already checked off their list. "I know my friend Adam likes horror movies, so if I want to see a good horror movie, I can look at the list of movies he's seen previously or wants to see." While browsing lists, you can like, comment on, or even "re-list" an item, which copies it to one of your lists.

After testing Well for a few weeks, I noticed that many people created the same kinds of lists, like Books to Read, Movies To See, and Stuff To Eat. Sarkissian understands that most people only keep these kinds of lists, but hopes that over time people come up with other creative ways to use the service. He imagines Well becoming a place where people create a list like "New York Trip" and friends chime in with things they've done that you might be interested in. You can of course create private lists as well for things like groceries, so Well can be the one place you keep to-dos for everyday items, but the service focuses on community. "We called the app Well in part because a community draws from a well," designer Addison Kowalski says.

The community aspect of Well is ultimately what makes it stand out. Plenty of apps like Astrid allow you to create collaborative to-do lists, but those kinds of apps generally focus on productivity-related to-dos. Well focuses on fun things to do and presents them in a beautiful and minimalist interface that's also accessible on any computer. You can follow other users, create cover photos for your list, and suggest items inside the lists of others. You can also create collaborative to-do lists between you and a few friends for planning an upcoming trip, or keeping track of things you need to buy for your college house. And finally, like Instagram, you can explore popular lists and draw inspiration for things to do.

Well is yet another free app that hopes to someday monetize, but Sarkissian actually has a pretty interesting idea for doing so. He hopes to eventually help you accomplish your goals in a new city, while cooking a new meal, or in seeing a new movie. "Between 60 and 70 percent of to-dos in the app have purchase intent as a part of them," Sarkissian said. At that point, it's just a matter of helping people find what they're looking for. Until then, Well is an elegant cloud to-do platform that lets your friends add crucial context to any list of things you want to do.