HTML 5 Examples

section represents a generic document or application section. It can be used together with the h1, h2, h3, h4, h5, and h6 elements to indicate the document structure.
article represents an independent piece of content of a document, such as a blog entry or newspaper article.
aside represents a piece of content that is only slightly related to the rest of the page.
header represents a group of introductory or navigational aids.
footer represents a footer for a section and can contain information about the author, copyright information, et cetera.
nav represents a section of the document intended for navigation.
video and audio for multimedia content. Both provide an API so application authors can script their own user interface, but there is also a way to trigger a user interface provided by the user agent. source elements are used together with these elements if there are multiple streams available of different types.
dialog can be used to mark up a conversation.
hgroup represents the header of a section.
figure can be used to associate a caption together with some embedded content, such as a graphic or video.
embed is used for plugin content.
mark represents a run of marked text.
progress represents a completion of a task, such as downloading or when performing a series of expensive operations.
meter represents a measurement, such as disk usage.
time represents a date and/or time.
ruby, rt and rp allow for marking up ruby annotations.
canvas is used for rendering dynamic bitmap graphics on the fly, such as graphs or games.
command represents a command the user can invoke.
details represents additional information or controls which the user can obtain on demand.
datalist together with the a new list attribute for input can be used to make comboboxes.
keygen represents control for key pair generation.
output represents some type of output, such as from a calculation done through scripting.

source: http://dev.w3.org/html5/html4-differences/#new-elements

So, all these fancy new tags...