Zipcode based search

I want to make a geographical search using US city and state or zip-code and corresponding results will be viewed. In the search we have to mention the radius distance. For example: i would like to search between 25 miles around California.

To do this, what should i do? is there any database containing us city,state,zip, latitude, longitude information?????

Please help me with this asap

with regards Tarek Mahmud Apu

From stackoverflow apueee

• For zipcode-based geolocation, see http://code.google.com/p/zip-code/ for example.

  From Alex Martelli

• GeoNames

  The GeoNames geographical database covers all countries and contains over eight million placenames that are available for download free of charge.

  There is also a webservice.

  From Karsten

• Once you convert your zip code data to longitude and latitude, here are a couple resources for working with the coordinates.

  Converting miles to degrees longitude and latitude

  Computing distance from longitude and latitude

  apueee : thanks for the link. those helping me lot
  From John D. Cook

• Free zip code database with lat/long coordinates at:

  http://www.populardata.com

  From $pageUsers[$post.author].name