Where to get geography data?

I need geography data for new website.

Data required is

States (With names and standard abbreviations)
ZipCode (List of zip code with all available data like where zipcode belongs to)

What would be my best source to get this data?

Any help is appreciated.

Thanks for all answers,

Sorry i went offline for fewdays. Yes i am talking about US zipcode data.

I think postal service data most reliable I will go with that.

Other alternative mentioned has similar and in better format data. but i think going with postal service will be the best option

Solution

(US assumed, "zip code" sort of implies the US 5-digit code, whereas "postal code" is the generic term)

States and their abbreviations are easy, it's on the Postal Service website. (including Guam & other parts of the US that aren't states)

Zip codes: the Postal Service would be the authority in question, but it looks like they don't offer the basic database of zipcode <-> town, other than through an interactive one-by-one lookup. They do offer street-level zipcode databases and other information for $ale. However the Census Bureau has a nearly identical set of information available. (ZCTA = ZIP Code Tabulation Areas) This has also been prepackaged more easily in a Sourceforge project (in their forum they claim this is from the Census Bureau data).