Determining a user's ZIP code

[]|V|[agnus]

I'm working on a coupon site where the users are to have the ability to search for all offers for businesses within' a certain distance from the user.

I was thinking it'd be a neat little touch if the field for their ZIP code were already filled in. It's my understanding that certain geographical information can be determined by doing a WHOIS on the IP address.

So I'm wondering if anybody knows of existing solutions to my problem that I could be directed to. I just found out about http://xmethods.com/ today while reading a tutorial on how to create a basic WHOIS webservice. I'll keep looking around there, but any addition help on this matter would be awesome.

[Span]

No... you can't find a user's ZIP code by doing a WHOIS. They have to type it in. For example, a WHOIS lookup on my own IP says I'm in Amsterdam. Well that's close if you like to walk a day or so. 50 km. And don't even think of trying to find the ZIP code of an AOL user..

[]|V|[agnus]

Haha, cool. Thanks.

[Noodles24]

The best you can do is something like this:

http://www.maxmind.com/app/areacode

But I wouldn't try second guess users, just let them type their own ZIP code in