Little side applications are fun to make. Try thinking of add-ons to your favorite current apps/websites to make them even better and you can make your own project! Or these are great tools to incorporate to make something else new and cool. I love adding JS libraries and APIs from other people and places to make use of the awesome things people put out into the web to share.
Of course, Google. Google drive? Email self a document = upload to drive? Oh the million possible projects using Google..
https://developers.google.com/apis-explorer/#p/
Unfortunately, google does not have a free API for translating anymore (you have to pay..).. but Microsoft does! I used this in my AnkiTranslate project. Good for if you want to work with multiple languages or make study aids to learn another language.
https://www.microsoft.com/translator/api.aspx
Can I say wheel of lunch? Lunch picker? Thing to do picker?
https://www.yelp.com/developers/documentation/v2/overview
Practice stock market = $$$.. if you can get good at it.
https://code.google.com/p/yahoo-finance-managed/wiki/YahooFinanceAPIs
And more..
http://www.quora.com/What-are-some-cool-fun-APIs
http://www.computersciencezone.org/50-most-useful-apis-for-developers/
http://www.webdesignerdepot.com/2011/07/40-useful-apis-for-web-designers-and-developers/
