There are multiple vimrc files, one per type of programming style - Wordpress, Drupal, CodeIgniter, Zend, and Ruby. If there are others that interest you, feel free to create it and I'll add it.
To use the WordPress vim file, use the wpvi alias when opening a file
$ wpvi functions.php
The HTML vim file that is load by all the others vim files.
It helps you write your markup consistently. Vim uses abbreviations to make reduce your typing. Each HTML tag has an associated abbreviation. It's not just HTML though. PHP code and phpdoc blocks.
To create a piece of code or markeup like '<title></title>', just type 't_title'.
In short, the formula is html tags is 't_' + tagname. html entities have the formula 'e_' + name.
Here are a few examples
e_copy
e_pound
e_currency
e_ellipsis
php control structures have the formula 'c_' + name.
c_if # will create an if block
c_ifelse # will create if/else blocks
c_while # will create a while loop
c_function # will create a function
phpdoc codes have the formula 'x_' + name.
x_package # will create a package phpdoc block comment
x_function # will create a function phpdoc block comment
x_method # will create a class method phpdoc block comment
Take a look at the vimrc files to see everything it can do.