HTTP status codes as haiku.
A site that has different gardening-related pictures depicting each HTTP response code.
binlist.net is a public web service for looking up credit and debit card metadata.
The first 6 or 8 digits of a payment card number (credit cards, debit cards, etc.) are known as the Issuer Identification Numbers (IIN), previously known as Bank Identification Number (BIN). These identify the institution that issued the card to the card holder.
Requests are throttled at 10 per minute with a burst allowance of 10. If you hit the speed limit the service will return a 429 http status code.
A canonical list of HTTP status codes (and what they're used for in a RESTful context), what they mean, and how they should be used.
Give it an identifier or serial number for a Compaq, Dell, Fujitsu, HP, Insyde, Phoenix, Sony, or Samsung laptop, and it'll generate a backdoor passcode to get into the system settings.
A Frequently Asked Questions file about phonetic alphabets. Covers the phonetic alphabets of multiple countries and military forces.
The Wikipedia page describing all of the known more-or-less standard HTTP status codes. Useful for people developing web applications.