There is a few couple of Ubuntu services (or subdomains). Not all of them is strictly developer-related:

Ubuntu Pastebin - http://pastebin.ubuntu.com/

Official Ubuntu Pastebin

Ubuntu Wiki - https://wiki.ubuntu.com/

This may be obvious...

Ubuntu Official Documentation - http://help.ubuntu.com/

This may be more obvious...

Ubuntu Brainstorm - http://brainstorm.ubuntu.com/ ^shutdown

Submit your Idea for Ubuntu here

Ubuntu Forums - http://forums.ubuntu.com/

This leads to the Official Ubuntu Forums.

Planet Ubuntu - http://planet.ubuntu.com/

A blog for Ubuntu developers written by Ubuntu developers.

Ubuntu App Developers - http://developer.ubuntu.com/

A site for Developers that develop apps for Ubuntu.

Ubuntu Mailing List - https://lists.ubuntu.com/

You can subscribe stuff about Ubuntu here.

Ubuntu Fridge - http://fridge.ubuntu.com/

An Information Hub for the Ubuntu Community.

Ubuntu Error Reports - https://errors.ubuntu.com/

Error reports about Ubuntu goes here.

Ubuntu Harvest - http://harvest.ubuntu.com/^shutdown

Harvest makes it easy to find low-hanging opportunities in Ubuntu. It aggregates the mass of todo lists we use every day so it's simple to find and coordinate work.

Ubuntu Single Sign On - http://login.ubuntu.com/

Manage your Ubuntu SSO account here.

Ubuntu Status - http://status.ubuntu.com/

This page shows the progress towards completing all of the Topics for the current cycle.

Ubuntu Apps Directory - https://apps.ubuntu.com

All apps in the Ubuntu Software Center

Ubuntu Developer Summit - http://uds.ubuntu.com/

UDS Official Website

Ubuntu CD Images - http://cdimage.ubuntu.com

All Ubuntu ISO's - From Warty to Quantal

Ubuntu Packages - http://packages.ubuntu.com

Information about Ubuntu's Packages.