This simple Chrome extension defaults Paypal's payment option to credit card.
This Chrome extension adds a limit of 140 characters to Google Plus and hides the buttons for doing fancy things that wouldn't be possible on Twitter, like recording video. In the interests of exceptional yet subtle UX, the HTML5 Audio API (via Buzz!) is used to play an airhorn effect when the user exceeds the character limit, and an image of the Dalai Lama flashes on the screen to remind the user of the beauty that can be found in simplicity.
(Sadly, some updates are required to make this work again after the latest Google+ redesign)
A (failed?) attempt to showcase the poetic form of trademark regi strations. A trademark viewer that displays only marijuana-related t-shirt designs, many of which are amusing when described in the painstaking detail recommended for registrations. Data retrieved via tess-search.
I built a fun little April Fools joke at Huffington Post - a paywall that only targeted visitors with New York Times IP addresses. There were some interesting challenges to the project due to CDN-level caching, so the IP detection was written using Akamai ESI.
Relying on a minor security issue in About.me (which I reported and has since been fixed), this permitted users to change the font on their About.me profile to Comic Sans.
A series of audio Captchas are added one by one, then slowly removed, creating a chorus of strange voices and an impossible Captcha challenge. This sounded a lot prettier before Google last revised its audio Captcha format to defeat automatic solutions.