I'm new to this forum, so I do not know if this has already been mentioned.
Modules. It was available in MovableType, but I couldn't find anything on modules when I switched to WordPress.
What are modules? They are little snippits of codes used commonly on multiple pages. For example, if I want to put an ad on my website, in order to add new ads, I'd have to go through every page and add the ad. Here's where modules come in. I create a module with the ad in it. Then I use a tag such as <module="theAd"> on every page where I want the ad. If I want to change the ad, all I have to do is change the module, and the module will be reflected on all the pages. Makes sense?
If anyone knows of a feature like this that I have not discovered with WordPress, please let me know at firstname.lastname@example.org . Thanks!