- <command> is used to define a button, such as a radio button, or check box. It must be used inside of a <menu> element.
- <article> is used to define an article from an external source – news site, blog, forum, etc.
- <datalist> defines a list of options, such as a drop-down menu. This tag is used in conjunction with the <input> tag.
- <dialog> is used to define a dialog or conversation.
- <embed> defines external content or plugins. This element has been used in previous HTML versions but is now re-introduced as an HTML5 standard.
- <figure> is used to represent flow content, separate from the primary content of a document. Additionally, the <figcaption> element is used within <figure> in place of the older <legend> element.
- <meter> is used to define a scalar measurement within a known range. For example, think of this as a representation of a “2 out of 10″ score.
- <time> represents time on a 24-hour clock, or a date in the proleptic Gregorian calendar.
- <source> is used in conjunction with the new media elements, <audio> and <video>, to define multiple source files.
- <ruby> defines a ruby annotation – Chinese notes or characters. <rt> is a child of <ruby> and is used to define the explanation of the ruby annotation. <rp> is used for browsers that do not support ruby annotations.
- <mark> represents a run of text in a document that has been marked or highlighted due to its relevance in another context. This new element is similar to the existing <strong> and <em> elements, though it is only used in terms of relevance and not importance or emphasis.
- <progress> defines the completion amount of a task. This could be used to display the download progress of an object.
- <keygen> represents a key pair generator control. When the control’s form is submitted, the private key is stored in the local keystore, and the public key is packaged and sent to the server.
- <output> defines the result of a calculation, such as output written from a script.
- <details> is used to show details about a document, or parts of a document. A user can obtain information or controls from this element. <summary> is a child element to show the summary/control of the <details> element. Think of this as an expanding area where the summary is a cickable link to “See more information.”
- <hgroup> is used to group a section of headings (<h1> – <h6>) when there are multiple levels of headings (primary heading, subhead, tagline).
The HTML5 standards draft is not 100% finalized as of the publish date of this post but is close to completion. The current draft of the proposed new standards can be viewed at http://dev.w3.org/html5/spec/Overview.html.