Well not ALL cards work. Most do.

There is a difference between a DVB card and a TV card. So make sure you know which one you want.

DVB = digital satellite broadcast ( like a reciever ).

TV tuner = only for normal ground broadcast ( like a TV ).

The ones usually available in the market are "lifeView" brands. These cards are divided by their chipset. I personally tried TV cards that are based on the "bttv" and "saa7134" and they worked ok (these are also the names of the kernel modules). Sometimes the cheap versions of these cards can not work with autodetection of the tuner type ( another chip on the card ). So you have to pass the tuner type as a kernel module parameter. The kernel documentation is your refrence here.

For DVB cards avoid "Twinhan" cards like the plague. They will freeze your computer at startup if you are using recent kernels like 2.6.10 or .11 ( This is my own personal experience ).

Check the different available Hardware compatibility lists to be sure before buying anything:

http://www.linux-mandrake.com/en/fhard.php3

http://bugzilla.redhat.com/hwcert

http://www.linux-tested.com

http://www.linuxhardware.net

http://www.linuxquestions.org/hcl/index.php

http://cdb.novell.com

Mythtv is not a TV tuning program. From the mythtv page : "MythTV is a homebrew PVR project". This means it manages recording and streaming for example using other tools.

"xawtv" is the standard tv tuner , but I don't like it.

http://linux.bytesex.org/xawtv

"tvtime" is a very good easy to use tvtuner.

http://tvtime.sourceforge.net

"mplayer" has good TV tuning capibilities but the its command line is hell.

http://mplayerhq.hu/homepage/design7/news.html