yelselthose ones are shit.
i bought this one about a year ago at walmart and it still works perfectly. sound is like you're listening to the radio. no problems at all and you can charge your cell as well
http://www.walmart.com/ip/Griffin-iTrip-Auto-Universal-Plus/17188990
Yea but the problem with those is that as you travel into different radio areas the station you are on gets fucked up and you gotta switch it to another empty station. With the tape one I have, it works perfectly.
OP see how much it is to install a cassette player? And don't use headphones even if you are driving by yourself. Shits not safe.
But if you can't do either of that, just use a cigarette lighter one like Yesel posted.