One of the very first things I do when installing a WordPress blog is to hack the titles. By default the page titles that WordPress generates are not SEO friendly, and the individual post page titles put the title of the post after the blog and archive wording.
The all in one seo pack plugin allows you to modify the blog’s meta tags through the WordPress admin panel as well as on the individual posts through the post editor. Its defaults are sensible and it represents a cleaner solution than hacking at the code to do it yourself because of the abstraction gained through the WordPress plugin architecture.
It’s now part of my standard WordPress install and should really be a part of the core software.