Here's an excerpt from the Omeka announcement:
The Okapi theme enables Omeka users without expert web design skills to create polished multimedia exhibits and collections. The home page features a cinematic 980×500 pixel main image and up to four featured exhibits. Exhibit pages include new layouts for articles, themed collections and embedded multimedia. The bundled Multimedia Links plugin enables embedding of HTML code, flash video (flv), and many other formats supported by the included JWplayer. The theme displays accessible Flash-based typography and is W3C CSS and XHTML compliant.