3state

/ – home or front page dep on setting
/home – post page, or latest post dep on settings and permalink structure.
/tag/<tag-name>[/<post-name>] – tag search or a post if <post-name>
/category/<category-name>[/<post-name>] – cat search or a post if <post-name>
/<cpt-name>[/<post-name>] – cpt presumably the same queries url mappings that apply to posts apply to the cpts under this path.
<anything>?s=<anything> – search
<anything>?p=<anything> – post with id
<something>/page/<n> or <something>/<n> – nth page of something.

There is a bunch more possible queries see http://codex.ww.wp.xz.cn/Using_Permalinks. This page describes how WP writes URLs by default. However all the possible combos must be valid as queries top (because they must be permanent). Note that all these queries only apply to posts (and possibly CPTs under <cpt-name> have not tested yet) and NOt pages. pages are always refed by /<post-name>. If there is a collision with a actual post (a post_type=post, post) then page takes precedence.

Horay!