For the new year's eve, I went with my wife, my friends and friends of my friends to a friend's grand-parents house in rural Portugal. We started planning early, however, although gmail makes a great job at organizing threads, we quickly had scattered data all over the mails thread (we were like over 15 people). This wasn't coordination (disclosure: I've seen wikis in plain english more than fifteen times on the commoncraft show ;) ). So, I decided to create a wiki at jottit to organize the trip. I like jottit because it's soo simple, but any wiki should do the trick. But I always keep in mind that simplicity in the wiki markup is crucial if I want for my friends to contribute (nearly no one was a programmer. In fact, most of us were from physics).

I started the main page with a quick how-to video, a list of people and the days they would attend, etc... Later, I also embedded a map in a page with directions for the place and a page to organize lifts, so we wouldn't bring too many cars (more than necessary). I got the place in the map wrong, but my friend providing the house corrected that quickly in the next version.

Also, another thing that was unthinkable, if it were not for the wiki, was to provide a complete menu of collaborative meals, where each one could enlist and contribute to the meal, by bringing tools and ingredients. We got menus for every meal, and it worked out alright, it was fun, it tasted good (I made a french ratatouille), and no redundant stuff was brought, and nothing really important missed. The only left-overs we had were bottles of portuguese wine (nice) and some vodka (yuk).

Finally, the most enjoyable thing is, probably, the wiki that's left for later souvenir of the good times we had. We put there afterwards our photos and even some videos! And last, but not least, we added a very useful lost&found section ;)
What a great experience! I really recommend a wiki for planning better trips with friends.