Does such a thing exist and is it free?
As a new father with lots of mates who ride bikes i was thinking how handy it would be if i could see quickly if someone was free for an hour and vice versa.
If not can someone please invent one? 
Would need to be private so burglars don't know.
Although it wouldn't stop your 'mates' nipping round for a quicky with the wife!
Google Calendar and invite who you want to see / add to it.
Rapha have an app that tells you about ride in your or any other area. You can also set up groups on there.
Doodle.ch is good for diary matching - requires manual updating from each participant but is about an elegant solution as I've found so far.
Cheers guys, i'll have a look at them. Already on gmail so that should be easy. Doodle looks good though, is it free?
Tis free
Try the rapha app if you've got an iPhone if not, and you all use Microsoft outlook then you can share your calendars.
