In case you didn’t know, the filters and action hooks API is the glory of WordPress: it’s what makes WordPress so easily modified and extended. Seeing which are the most often used should say something about what plugins in general are trying to do.

I think the most interesting result of Dale’s survey is that so few are used frequently. Once you get past the action hooks that have to do with plugin/widget initialization and the filters of post text, few remaining are statistically significant. That suggests to me that most plugin developers are under-utilizing WordPress’s full potential.

See Dale’s results here.

By default, this admin bar looks a lot like the one at WordPress.com, but it (optionally) includes all available admin menu items, and there are a number of built-in styles, or “themes,” to choose from.

Viper007Bond contributes quite a bit to WordPress core development, so as one would expect, this plugin is coded well: the code itself is clearly organized, it follows WordPress standards with regard to localization, it’s even forwards-compatible with some features of the next version of WordPress, and it’s extensible: he’s provided a feature that allows themes to add their own admin bar “theme.”

Typically, if you paste content from Word into WordPress’s WYSIWYG, TinyMCE, you get a ton of unsightly markup, such as font and alignment tags, which can wreak havoc on your site’s appearance. Users can get around this by enabling the advanced features of TinyMCE (click the “kitchen sink” button on the far right) and pasting using the special “Paste from Word” button, but the problem with this is that the kind of people who usually have a problem with this (using Internet Explorer, TinyMCE, and writing blog entries in Word) are not typically the most tech-savvy folks, so finding and remembering to use the “Paste from Word” button can be difficult. For a number of end users I’ve written regex replacements that do the same thing, so this plugin is a welcome addition.

In case you don’t know, Plurk is like Twitter, except that it has a slicker UI, with your Plurks and those of your friends floating across the screen in a timeline.

Unlike the others such as Akismet, TypePad AntiSpam, and Defensio, Mollom alters the comments database table to add a field. I don’t usually think that’s a good idea, but other, popular plugins do it.

Curiously, none of TypePad, Defensio, or Mollom uses text localization, so they must not be planning to offer versions in languages other than English.

Michael Arrington of TechCrunch has tried it and claims that it has fewer false positives than does Akismet.

RefTagger works on any sites that use its JavaScript, but the Logos page includes WordPress plugin that does this automatically.

1. Use wp_enqueue_script() to load external libraries and standalone scripts, instead of generating your own script header tags.
2. On admin pages, use the admin_print_scripts-[mypage] action hook to register the code on only your plugin’s page, not every admin page.

Both of those techniques have been available since WordPress 2.1, so plugin authors can be pretty confident that there will be no backwards-compatibility issues in employing them. (Despite the fact that WordPress is maintaining the 2.0.x version line until 2010, my research suggests that the number of users of that branch is insignificant.)

I would add one more tip to Ozh’s: don’t pollute the global JavaScript namespace, especially with the over-used “$”. A number of JavaScript libraries use the dollar sign in different ways, so you can run into problems if, for example, you’re using jQuery but another plugin has loaded Prototype.

Fortunately, jQuery makes it easy to use “$” in a friendly way with other libraries. My favorite is to wrap jQuery-based code in something like the following, which employs $ outside of the global namespace and waits to execute the script until after the DOM has loaded.

jQuery(function($) { /* some code that uses $ */ });