25th
From the creators of the ultrasimple todo list.
Wikipedia search fails for the simplest of spelling mistakes. This Greasemonkey script adds a “Did you mean” option to Wikipedia search. Install it here.
This Firefox extension adds a right-click context menu option “Pronounce” to every word.
I’ve always found it difficult to follow Twitter conversation threads. So I’ve written a Greasemonkey script to automatically retrieve and display nested replies. The script recursively follows the “in reply to [user]” and gets the entire conversation thread. Install it here.

Note that Twitter links replies to the last update made by the original poster, so some threads may appear broken.
A Boss Key, a keyboard shortcut to quickly hide a computer game and display a fake work screen, used to be a fairly regular feature on DOS based games.

Panic is a similar Firefox extension which closes all open tabs, and replaces them with a Google search for “Increasing Workplace Productivity”.
Google has a neat transliteration tool, which allows Hindi (or other Indian scripts) to be typed using the English alphabet. For instance “mera” is transliterated to “मेरा” (Hindi font support needed)
I’ve used that to write gIndic, a Firefox extension which provides transliteration service on any website. Like the Google service it supports Hindi, Tamil, Telugu, Kannada and Malayalam. It works on both Firefox 2 and 3.
You should now see the gIndic icon - the letter “A”. To start transliterating, click on the “A” icon and choose your language. Click on “A” icon and choose the “Default” option when you want to type in English again.

Type a word and hit a space to translate it. It works on input and textarea tags.
Firefox seems to have a neat undocumented function find ().
When called without parameters - find (), it opens the find dialog box. With a parameter - find (‘firefox’), it searches and focuses on the first found string.
Phonewords (vanity numbers) are the alphanumeric equivalent of a numeric telephone number, made up from the various letters of the alphabet that correspond to particular numbers on a telephone keypad.
Comprehensive list of Windows Freeware utilities, a lot of them “better than their commercial alternatives”.
Converts images to an HTML table with large number of background coloured 1x1 sized cells.
Using the robots.txt protocol, Indiatimes has blocked out all web crawlers from accessing its contents.