I have not tried this one out yet but it does seem very promissing. Many people have left some great reviews. Althought they ask for the code not to be changed or redistributed , so im not sure how this falls into the open source category. hopefully they will change that soon and i can look at the code and see if we can integrate it into other things.
Here is a list of features it has
Advertisement Addon
Turn orders on/off
Turn instant activation on/off
Admin Levels (Root, full and limited)
Root admins choose what limited admins can access
Private Messaging
User Control Panel
Newsletter Manager
Email Templates
Admin Notes
Latest Script News
Order Statistics
IP Whois
List Accounts
Orders Management
PHP Info Page
WYSIWYG Editor
Signup Statistics
Search Orders
Forgot Password
Remember Me option
MD5 Encrypted Password
IP Banning
IP Orders
IP Restriction
Script Details
Signup Keys
Used Signup Keys
Package Management
Domain Management
User Admins Management
Suspend/Unsuspend Accounts
Send Emails
Support Request
Configuration Page
Email Configuration Page
TOS Configuration Page
View/Delete Logs
