As soon as i install WP on any site I install
Advanced admin menus its brilliant! It makes all the sub links in WP a drop down menu so you don't have to click twice to get onto the theme editor page - a life saver if your connections as rubbish as mine!
I also love the full text feed plugin,
Full Text Feed · cavemonkey50.com I can't stand cut off RSS feeds.
The sideblog WP plugin is great if you have little things to say but don't want a whole new blog post!
Sideblog
Spotmilk makes the admin interface pretty -
CeprixConception | SpotMilk, Admin Theme for WordPress
I also have a soft spot for WP-grins!
WordPress Plugins | alexking.org