So you have WordPress installed! Congratulations! Now what? I find myself installing WordPress quite often, so I'll share with you my "first steps" after a fresh install to get WordPress set up to my liking. This involves changing settings, resetting the theme, and some universally useful plugins.
At the time of this writing, WordPress 2.6.5 was just released. You know, "for future reference".
Remove the default "admin" account
I don't feel comfortable leaving an account in WordPress with a name that every single other WordPress blog in the world started with, even if it does have a secure password. Go under Users and add a new account with Administrator level privileges. Then Log Out and log back in with the new account.
Now you can go back under Users and delete the default "admin" account. The default "Hello World" post has "admin" as its author, so you'll be warned when deleting that user and asked what you would like to do with that post. Might as well just re-attribute it to your new user.