If you are having audio problems on a Linux system, your first step is to ensure that the userid you are logged in as is a member of the "audio" group. I have been using Linux for years, and if it has been a while since my last install, this one still causes me several minutes (or more) of head-scratching every install.
There are several issues that make sound on Linux desktops a source of pain and frustation:
"USB Sound" to the rescue!!!
USB sound tends to be relatively simple and robust. I have tried four devices so far (two headsets, a pair of USB speakers, and a "USB sound card") and all of them have worked. For the three devices with microphone capabilities, that also worked. Mixers show one slider / mute button each for input and output -- dummy proof!!
A USB sound device, when plugged into a system with a functioning onboard sound card, behaves like a second sound card, and does so consistently on whatever computer you plug it into, freeing you from dependence on your internal sound card. It shows up explicitly in Skype Options as a a second sound card, input/output levels are easily adjusted in your mixer, and the three models I have tried:
all work well with Skype, though sound quality from #3's mic is a bit poor (probably fixable with a higher quality mic....)
Using a USB sound device with other Linux multimedia applications tends to be a bit more complicated, since such apps (Skype excepted) do not usually provide a sound card selector in the GUI. Here are some examples of how to send sound output to a second (USB) sound card for several applications:
Simplest of all, disable the built-in sound card by blacklisting the driver module, as I did with my Thinkpad x20. Then when you plug in a USB sound device it automatically becomes the first and default sound card, which all apps will then play sound to by default. (Note: I looked for a more elegant way in Debian, but found none. Please clue me in if you know a better way. I have heard that Ubuntu automatically does the right thing by making a new USB card the default. In the case of the X20, the built-in speakers really suck anyway.)
Where I live in Beijing a low-end USB sound card (looks like a USB memory stick / thumb drive except that it has headset and mic jacks in the end) can be had for as little as 25 RMB / US$4. I have a beautiful pair of tiny, mega-sound USB speakers (with no external power supply!! power comes from the USB bus!!) that I paid 140 RMB for, as I recall.