I mentioned that, after installing openSUSE 11.0 on my laptop, I found that sound wasn't working. It turns out that there are some bugs with the new 'pulseaudio' audio software that openSUSE uses. In spite of that, after some playing around and searching the Web, I seem to have sound playback working with both speakers and headphones. Skype is also working (so the microphone works too). The things I did were:
went to “Computer | Control Center”, selected “Sound”, and set all of the drop-downs to their “ALSA” options;
started the GNOME volume control from the command line using “gnome-volume-control” and used that to set the sound levels;
in the Skype “Sound Devices” settings, set the “Sound In” to “HDA Intel (hw:Intel,0)” (your own microphone setting may differ from this, but don't set it to “pulse”). Set “Sound Out” and “Ringing” to “pulse”.
Having to start the volume control from the command line was unexpected, but the volume control crashes if you try to open it from the volume control applet, so it's what you have to do. Not ideal, but so much better to have sound working than to have no sound at all.