Iusethis contact system.
One of the things we've mentioned as a reason to use iusethis is getting app recommendations from people you know. So let us show you how it works. Whenever you are surfing a contact's profile, you can choose 'Start following' from the menu. The user will now have a border around the avatar to indicate that it represents a contact, and if you go back to your profile, you can choose following, and the user will show up on that list.
So, how do you find your contacts in the first place? If you know the screen name, there's no problem. Just type it into the search field. You can also search for his email address. If your contact has registered on iusethis, you'll be sent directly to his profile. You can also click on the avatar in comments to go to the user profile, or click the count anywhere to see all the users that use a certain application. Finally, from your friends page, you can see who's following you by following the link at the bottom. (It will only show up if somebody marked you as a contact.)
On the right hand sidebar you'll see the latest apps your contacts have started using, and you can focus on it by choosing the more link below. There are also RSS feeds for your contacts' apps, so you can keep track of what new apps your contacts start using.