Catchup app
I was trying to organise coffee with a friend today and it was pretty irritating going back and forth about times. It's a problem that's come up a lot recently and I'm getting dangerously close to the point where I start making something to solve it.
So here's my first sketch for how it might look. Basically you enter emails of the people you want to catch up with. Then you get a calendar widget to choose what times to suggest. You can import your calendar to speed up the process, and if the other invitees are already in the system their calendars are overlayed as well so you can narrow down the times even more.
Then it generates some standard language like "I'm free all day Tuesday, Wed 3-5pm, Thurs 9am-1pm & 3-5pm. You can check out my full calendar here: http://site.com/link". When someone clicks the link they can narrow it down to their own availabilities. The point is that it interoperates well by allowing you to keep the discussion happening through email by default, but with the website augmenting the process so it should ideally only take one round trip.
I haven't made any particular steps towards this yet, but give it a few more catchup discussions and I'll probably get cranky enough to do it.