Xine is a very popular multimedia player for Linux. Before all, it's a movie player, but it also can play audio files or connect to live streams. DVB cards can be accessed using the dvb input plugin.
In Debian/Ubuntu etc
apt-get install gxine
Then create the channels list using the dvbtools' scan
mkdir ~/.xine scan >~/.xine/channels.conf
Now start up gxine
and open the DVB card with
File -> Open MRL -> dvb://
You should now see a program. You should be able to zap around using the NumPad-9 / NumPad-3 keys, the xine playlist, or using the next/previous chapter buttons in your gui.
- xine Digital TV (DVB) - Howto use xine for DVB