I needed to configure ALSA on Sarge because I wanted to use Ekiga Softphone and although it supports OSS but the support is not good. It was fairly straight forward process to do that:

ajitabhp@fimbles:~$ sudo apt-get install libesd-alsa0 \ 
gstreamer0.8-alsa esound-clients alsa-base alsa-oss
ajitabhp@fimbles:~$ sudo alsaconf

In the alsaconf screens I answered all the defaults. And once I was done, under the menu item

Applications→Desktop Preferences→Advanced→Multimedia Systems Selector

I changed the default sink and default source to ALSA and Pipeline to alsasink and alsasrc respectively.