The Digg Application Programming Interface (API) has been created to let users and partners interact programmatically with Digg. The API returns Digg data in a form that can be easily integrated into an application or a web site.

See the documentation at http://apidoc.digg.com/

Here's some interesting parts from their docs:

Be Polite, Please!

Use good judgment when designing your application. Don't make repeated requests for the same data frequently. […] We monitor API usage, and we may block applications that do silly things.

They also launched a contest for using this API.

With the AJAX Feed API, you can download any public Atom or RSS feed using only JavaScript, so you can easily mash up feeds with your content and other APIs.

It requires JavaScript knowledge to integrate with any website, but it's all documented by Google and not hard to do.

If you're a web developer or host, you may remember that we introduced you to the AdSense API last May. With the AdSense API, your users can create their own AdSense accounts on your site, and display ads alongside the content that they have created. They can also manage their accounts and view ad performance and earnings reports, all on your site.

…

Today, we're pleased to announce that the AdSense API is now open for all developers, with the release of our open development sandbox. This is a replica of the live service with some additional support to help you test and debug your applications. Once you implement the AdSense API in the development sandbox, we can go live with your implementation.

Using this API you can share advertising revenues with creating content online users without webnasters worrying too much about accounting and money, all managed by Google. It looks liek a win-win situation for everybody.

Some already fear that AdSense API will skyrocket click-fraud. However this is a sample account creatin using PHP straight from their online documentation:

<?php

// Copyright 2005, Google Inc. All rights reserved.

/**
 *  sample code to create an Adsense account through Adsense API
 */

require_once('lib/nusoap.php');
require_once('common.php');

$server = 'https://www.google.com';
$namespace = 'http://www.google.com/api/adsense/v2';

// Set up the authentication headers
$email = '<impl:developer_email>REPLACE WITH DEVELOPER EMAIL</impl:developer_email>';
$password = '<impl:developer_password>REPLACE WITH DEVELOPER PASSWORD</impl:developer_password>';
$client_id = '<impl:client_id>NOT RELEVANT</impl:client_id>';

$header = $email . $password . $client_id;

// creating soap client
$wsdl = $server . '/api/adsense/v2/AccountService?wsdl';
$client = new soapclient($wsdl, true);
$err = $client->getError();
if ($err) {
  showSoapClientError($err);
  return;
}
$client->soap_defencoding = 'UTF-8';

// Set the headers; they are needed for authentication
$client->setHeaders($header);
if ($client->fault) {
  showMyErrors($client);
  return;
}
$err = $client->getError();
if ($err) {
  showSoapClientError($err);
  return;
}

// setting the parameter
$param = '<loginEmail>users_address_here@example.com</loginEmail>';
$param .= '<entityType>Individual</entityType>';
$param .= '<websiteUrl>http://test.aaa.com</websiteUrl>';
$param .= '<websiteLocale>en</websiteLocale>';
$param .= '<usersPreferredLocale>en_US</usersPreferredLocale>';
$param .= '<emailPromotionPreferences>true</emailPromotionPreferences>';
$param .= '<synServiceTypes>ContentAds</synServiceTypes>';
$param .= '<hasAcceptedTCs>true</hasAcceptedTCs>';
$param = '<createAdSenseAccount>' . $param . '</createAdSenseAccount>';

// invoke web service
showCall('createAdSenseAccount', $param);
$response = $client->call('createAdSenseAccount', $param, $namespace);
if ($client->fault) {
  showMyErrors($client);
  return;
}
$err = $client->getError();
if ($err) {
  showSoapClientError($err);
  return;
}

// get back the response
$response = $response['createAdSenseAccountReturn'];
showCreatedPublisher($response);

// showing the soap
showRequestResponse($client);

?>

Via ZDnet Blogs: yourminis opens up the widget platform, releases API

Tonight yourminis announced the availability of their API, giving developers a way to build widgets and upload them. In addition, the team released an analytics application that will help you track where your widget is going and how many people are using it. All of this is under a developers section on the yourminis page which includes information on how to get started and the files you'll need to download.

What are minis? They are personalized widgets for desktop or web sites made with Adobe Flash.

With the Yahoo! Mail Web Service APIs, you can build applications to perform tasks such as listing messages, displaying folders, and composing and sending messages.

Here's an authentication example from their samples:

<?php
// test.php — Test Yahoo! Browser-Based Authentication
// A simple auth exmaple.
// Author: Jason Levitt
// Date: November 20th, 2006
// Version 1.0
//

// Edit these. Change the values to your Application ID and Secret
define("APPID", 'JzkILqzIkY1xxxxxxxxxIaGILaRWClvO');
define("SECRET", '10de7e35xxxxxxxxxe5749207495ed');

// Include the proper class file
$v = phpversion();
if ($v[0] == '4′) {
include("ybrowserauth.class.php4″);
} elseif ($v[0] == '5′) {
include("ybrowserauth.class.php5″);
} else {
die('Error: could not find the bbauth PHP class file.');
}

function CreateContent() {

$authObj = new YBrowserAuth(APPID, SECRET);

// If Yahoo! isn't sending the token, then we aren't coming back from an
// authentication attempt
if (empty($_GET["token"])) {
// You can send some data along with the authentication request
// In this case, the data is the string 'some_application_data'
echo 'You have not signed on using BBauth yet<br /><br />';
echo '<a href="'.$authObj->getAuthURL('some_application_data', true).'">Click here to authorize</a>';
return;
}

// Validate the sig
if ($authObj->validate_sig()) {
echo '<h2>BBauth authentication Successful</h2>';
echo '<h3>The user hash is: '.$authObj->userhash.'</h3>';
echo '<b>appdata value is:</b> '. $authObj->appdata . '<br />';
} else {
die('<h1>BBauth authentication Failed</h1> Possible error msg is in $sig_validation_error:<br />'. $authObj->sig_validation_error);
}

return;
}

?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8″ />
</head>
<body>
<div id="look">
<h2>Test BBauth </h2>
<div>
<?php CreateContent(); ?>
</div>
<div id="content">
</div>
</div>
</body>
</html>

They also offers $10 commission for developers which refer clients to premium Yahoo! Mail account.

- Document your Web API completly, with examples.
Different providers offers documentation in different forms, more or less complete. Web API consumers rnage from gurus to beginners, and I suppose you want your API used by as many people as possible. A structured, step by step instructions with samples will help a lot.

- Create code repository for scripts based on your web API.
There are many people capable of writing good code based on that API they may want to share with others, maye open-source. Why not create repositories for these small projects?

They have a limit of 100,000 requests in 24 hours period. For details see online documentation.

I won't comment here too much about this new service, features or fees but mention new API. New Google Checkout API allows you a deep and secure integration with web/desktop apps. They offer samples for ASP (IIS), PHP & Java, with full documentation for each of these languages. Here's a link to PHP sample.

Files with their functions available for integration into your custom application are not trivial, but easy to understand. Give it a try and see if they are ok for your needs.

Geocoding is the process of converting addresses (like "1600 Amphitheatre Parkway, Mountain View, CA") into geographic coodinates (like latitude 37.423021 and longitude -122.083739), which you can use to place markers or position the map based on street addresses in your database or addresses supplied by users. The Google Maps API includes a geocoder that can be accessed via HTTP request or directly from within the JavaScript. 

This was something I was looking for to have a complete solution for displaying & using maps.