W3C have released the HTML 5 draft and you can check out the differences from HTML 4.

Heres a summary:

• More structural tags
  eg header, footer, nav, section, article and dialog (as in spoken dialog)
• Media
  eg audio and video
• Graphics
  The long awaited canvas drawing area….
• Additional input tag types
  eg datetime, number, range, email, url
• Programmer bliss
  2D graphics api, client-side data storage, content editing api (contenteditable) and a drag and drop api
• Gone but not forgotten
  Elements not used: acronym, tt, strike and dir
  Elements used too often to detriment: frame and frameset
• Programmer Gotcha’s
  Remember when bold was b and then changed to strong? Well b is now bold again and strong is importance! Applet is replaced with object.

Overall the feature inclusions are exciting even though they are about 5 years late.