Volume Control/Icon is gone (Ubuntu 10.04)
The alsa sound driver, and volume control icon don't always work in 10.04.
First, You may have this, or may not, but the Volume Control needs to be running.
Click on System>Preferences>Startup Applications
Click +Add, then input:
Name: Volume Control
Comment: Launch volume control applet
Next, The top bar panel needs the volume and login icon. It's done with something called Indicator.
(Someone else already asked why it's called "indicator" :) )
Right Click on Panel (Top Bar)
Click Indicator Applet
Click Add button
You may need to reboot to take effect.