I've just bought an external card for my future lappy, seeing as a line in socket is pretty rare for a laptop and the sound quality of a laptop usually isn't very good.
If you really need one (because your pc doesn't have a line in socket, or it's using a basic soundchip which isn't very good - as most aren't) then there's a Creative Sound Blaster Live 24Bit External USB 5.1ch / Remote available for about £40.
I've just bought a Creative Sound Blaster Audigy2 ZS Video Editor for £67, which has a good quality soundcard built in and will allow me to rip video and camcorder footage to my lappy
