AdultFriendFinder. All their ads guess my location and try to convince me that there are lustful women in my neighbourhood who are desperately looking for someone like me.

From Pullman, Washington, I have gotten AdultFriendFinder to claim I am in any of Post Falls, Idaho, Couer d'Alene, Idaho, and Overland Park, Kansas.

Yes, it isn't all that accurate. I did a cross-check with a few friends to see if the results matched the Maxmind free database. It seems they are using that.

http://goingtorain.com, I think.

http://rememberthemilk.com uses this to find out where I am, so it can show me tasks due at my current location.

Try: http://ipinfodb.com/ They offer a free geolocation API and even their SQL DB is free.

They've also spammed just about every social media site out there. Check out e.g. http://news.ycombinator.com/submitted?id=marchost

I can't figure out if you're actually trying to help, or if you're just a sock puppet for "marchost". The fact that this is your only contribution to HN does not ease my apprehension.

The only reason I made that post was because I've used their services in the past and never had a problem with it.

I certainly do not have any affiliations with "marchost" nor am I his sock puppet for anything (I've never even spoken to him/her).

Google (try a search for e.g. 'pizza delivery'). However if you have the appropriate cookies set, I believe it will use a remembered location rather than your IP-derived location. I don't know whether to consider this a feature or a bug.

I haven't seen anyone do anything I've found really useful. Most are like this one, that tells you how long the sun is over the horizon based on where you are: http://mersol.se/

Try http://ip2location.com/ . They've been around for quite sometime and IMHO it's more accurate than maxmind.

Google. Serving AdWords ads to you.

Well, actually its service ofered to their adveritsers.

Several job boards use GeoIP to show jobs near you first

maxmind, quova