The important bit of info here is a rough guess of how far we're talking about. 100'? 500'? 5,000'?
I've also got a 50' RCA run that I used to use to connect the laptop to my AV rack. Never had any problems with it. It works just as if it were a 3' cable.
And I'll second jakewash's suggestion - if you're looking for amazing prices on decent cabling, do check out Monoprice.com.
Here's a 100' RCA cable for $17.
But if you need a really long run, I don't know what would be best. If I were faced with the challenge, I'd probably first try to do it with bulk network Cat6 cable. That's designed for long runs anyway, so I'd guess that it would stand a chance of being able to pass the audio signal well enough. And since it's already 4 twisted pairs, you've got your +/- for both channels, all conveniently housed in one bundled wire, and twisted for good RF rejection. You'd just have to re-terminate the ends with RCA jacks, which isn't too hard. I don't know if that would work, but it's what I'd probably try if I had some monster run that I was trying to cable.
Something like
this, perhaps.
Edit: RG6 is an excellent idea too. That also is designed for long runs.
Good luck!
