You can have simultaneous sound in linux with ALSA (Score 1)

If you have sound with ALSA but only for one app at a time then it's not being mixed properly. You can set it up however, just configure your /etc/asound.conf to something like this:

pcm.card0 {
type hw
card 0
device 2
}

pcm.!default {
type plug
slave.pcm "dmixer"

}

pcm.dmixer {
type dmix
ipc_key 1025
slave {
pcm "hw:0,2"
period_time 0
period_size 2048
buffer_size 32768

rate 48000
}
bindings {
0 0
1 1
}
}

That is my asound.conf for optical out with AC'97 on a K8ne deluxe mobo. Of course yours will probably be different.
Also you need to configure your apps to use ESD (preferably) or alsa as sound output. Works like a dream in Ubuntu and has never crashed!