Here’s a useful list of resources on how to create an API, compiled from posts that were published recently on this blog. The included APIs can provide a fantastic ways to enhance websites.
1. The WordPress(WP) API exposes a simple yet powerful interface to WP Query, the posts API, post meta API, users API, revisions API and many more. Chances are, if you can do it with WordPress, WP API will let you do it.  With this API you can get all posts with specific search term and display it on your website or get text from all posts and do text analytics.
Here is the link to post that is showing how to Retrieve Post Data Using the WordPress API with Python Script
You will find there python script that is able to get data from WordPress blog using WP API. This script will save downloaded data into csv file for further analysis or other purposes.
2. Everyone likes quotes. They can motivate, inspire or entertain. It is good to put quotes on website and here is the link to post that showing how to use 3 quotes API:
Quotes API for Web Designers and Developers
You will find there the source code in perl that will help to integrate quotes API from Random Famous Quotes, Forismatic.com and favqs.cominto into your website.
3. Fresh content is critical for many websites as it is keeping the users to return back. One of possible ways to have fresh content on website is adding news content to your website. Here is the set of posts where several free APIs such as Faroo API and Guardian APIs are shown how to use to get news feeds:
Getting the Data from the Web using PHP or Python for API
Getting Data from the Web with Perl and The Guardian API
Getting Data from the Web with Perl and Faroo API
In these posts different and most popular for web development programming languages (Perl, Python , PHP) are used with Faroo API and Guardian APIs to get fresh content.
4. Twitter API can be also used to put fresh content on web site as Twitter is increasingly being used for business or personal purposes. Additionally Twitter API is used as the source of data for data mining to find interesting information. Below is the post that is showing how to get data through Twitter API and how to process data.
Using Python for Mining Data From Twitter
5. The MediaWiki API is a web service that provides convenient access to Wikipedia. With a python module Wikipedia that wraps the MediaWiki API, you can focus on using Wikipedia data, not getting it.  That makes it easy to access and parse data from Wikipedia. Using this library you can search Wikipedia, get article summaries, get data like links and images from a page, and more.
This is a great way to complement the web site with Wikipedia information about web site product, service or topic discussed. The other example of usage could be showing to web users random page from Wikipedia, extracting topics or web links from Wikipedia content, tracking new pages or updates, using downloaded text in text mining projects. Here is the link to post with example how to use this API:
Getting Data From Wikipedia Using Python