I have an iPhone application where i need to find out the current location(in terms of city name or probably the address). But i'm not been able to do that. I can find out the current latitude and longitude. Is there any web service(preferably free of cost) which can return me the current location name if i supply the latitude and longitude?
The feature you're looking for is called Reverse Geocoding.
Here is a list of web services that provide this function.
A couple of the most popular are Geonames.org, Google Maps Services API and Batchgeo.com for batch processing of multiple coordinates.