It's increasingly rare that you ever need a friend's physical address anymore, but there are occasions where you need to send out a physical letter. If you don't feel like emailing, calling, or posting a Facebook update to track down addresses, Postable is a dead simple and secure address book where your friends can enter their own info.
After you set up your account you receive a link with your address book. Send that link out to your friends and they can add their information. Your friends can only add their information. They can't see other entries in your address book and the site is secured. Once you get everyone's address, you can export your address book to Apple Address Book, Microsoft Outlook, Gmail, Excel, and even print labels.
Postable | via Swiss Miss
iOS: When you roll up to your friend's house, you usually go searching through your contacts to call them. Pocket Doorbell saves you a step by determining your location and calling your nearest friend with the tap of a button. 
Give simple, clever webapp 
iOS: Like Instapaper but for physical locations, Matchbook saves locations you want to visit for another time. If you see a restaurant you like or a cool shop you want to remember, you can simply open Matchbook and bookmark it for later reference. 
