Below is a list of the general user tags available in WordPress, sorted by function-specific category.

the_author

the_authior_description

the_author_login

get_the_author_login

the_author_firstname

the_author_lastname

the_author_nickname

the_author_ID

the_author_email

the_author_url

the_author_link (Version 2.1)

the_author_icq (Deprecated)

the_author_aim

the_author_yim

the_author_msn (Deprecated)

the_author_posts

the_author_posts_link

list_authors (Deprecated)

wp_list_authors