Zen Coding

If you haven't heard of it yet, and write HTML, you'll love this:

http://code.google.com/p/zen-coding/

it allows you to write something like this:

div#page>div.logo+ul#navigation>li*5>a

and get this by pressing <kbd>tab</kbd>

<div id="page">
        <div class="logo"></div>
        <ul id="navigation">
                <li><a href=""></a></li>
                <li><a href=""></a></li>
                <li><a href=""></a></li>
                <li><a href=""></a></li>
                <li><a href=""></a></li>
        </ul>
</div>

Has plugins for eclipse (https://github.com/sergeche/eclipse-zencoding) vim, emacs, text mate and sublime text 2