Social Networking on Drupal

Previously, I tried several open source social networking frameworks including elgg, aroundme, peopleaggregator... However, few of them are mature and stable. So I also tried Content Management Systems. I delved into Drupal.
Drupal is an excellent CMS which has many powerful modules. Some modules provide social networking support. There exists a drupal group which promotes social networking support in Drupal.
Here I list some useful modules which may be used in social networking:
Organic Groups
"Enable users to create and manage their own groups. Each group can have subscribers, and maintains a group home page. Groups get their own theme, language, taxonomy, and so on."

Buddylist
Allows users to add other users to buddy list, organize buddies into buddy group and monitor buddies' content.

Invite
Adds an 'Invite a friend' feature that allows users to send and track invitations to join a web site.

FOAF
Functionalities:
"1. automatically import/synchronize profile information between any Drupal-powered sites
2. import profile information from external FOAF files
3. export a FOAF file based on a user's profile"

Privatemsg
Allows users to send private messages to each other.

User Relationships
Allow users to create named relationships between each other.

Wiki
interwiki
This filter provides a simplified, wiki-like syntax for linking to articles or search results on many commonly-used internet reference websites
Liquid Wiki
The Liquid Wiki Engine Project aims to build a module providing wiki funktionality to Drupal.
MediaWiki
Integrate Drupal with an existing MediaWiki installation.

Online Chat
Chat Room
This module enables chat rooms to be set up on Drupal sites. No additional software is required. Chat Room uses AJAX to update chats without page reloads. Chat rooms are nodes that provide access to chats and chat archives.
BoWoB
Free Chat for your website, integrated with your Drupal users and design. It is implemented in Flash.