When I install WordPress for you, you get a bunch of pre-installed plugins. You also get to pick additional ones from the list below; these also happen to be some of my favorite plugins.
All in One SEO Pack
Category Posts Widget
Contact Form 7 ((With one basic contact form installed.))
Ozh' Who Sees Ad
Page Links To
SEO Smart Links
Subscribe to comments
WP Since Last Visit
WP-Polls ((Installation only))
WP-PostRatings ((Installation only))
WordPress Download Monitor
cForms II ((Installation only))
There are some plugins that require extra configuration. The plugins listed below can be installed for an additional fee.
wp-e-commerce ((Please note: This plugin is free, but desirable addons may be purchased directly from Instinct))
Featured Content Gallery
If you would like to add a plugin to the list, please speak up in the comments. I'll probably add it to the next revision of this list, or you can do it in private.