A few years ago, a group of my friends (who went to uni together and now live across the UK) were trying to arrange to meet up one weekend. A whole sequence of e-mails were sent suggesting days but we were struggling to find a day everyone could make. I spent a weekend starting to write a small web application that I thought would help. At the time I didn’t know any PHP so I didn’t quite finish it that week-end (and we ended up arranging to meet without it).
The application languished unloved for a few years, every now and again I’d spend an evening looking at it but all I would achieve each time was to learn my way around the code again.
For a few months now the application has been basic but usable and I’ve now registered a domain for it: WhenShallWe.com. You give it a few details about the thing that you’re organising, a little of possible dates and a guest list. It then email each guest a link to a web page where they can say which days they can make. It can make finding a suitable day much easier.