Since version 4.3 of Skype, alsa is no longer supported in favour of pulseaudio.
I need alsa because several USB webcams are known not to work with pulseaudio.
Where can I download the last Ubuntu .deb package version of Skype that still supported alsa?
The safest way to install Skype is from the Canonical Partner repository. The latest version there is still 4.2.
The advantage with getting Skype from Canonical Partner is that certain dependency packages are automatically installed.
Download version 4.2.0.13 of the .deb file and install it. (The Canonical Partner repository is still at version 4.2.0.11.)
wget http://download.skype.com/linux/skype-ubuntu-precise_4.2.0.13-1_i386.deb
sudo gdebi skype-ubuntu-precise_4.2.0.13-1_i386.deb
On 64-bit systems, one needs to be multiarch because Skype comes only in 32-bit on GNU/Linux.