The new software sees big (not mainly cosmetic) changes to the user interface and toolbar. Practical changes include Public Chats, so you can now join without being manually added by the chat host and the option for bloggers/webmasters to post a link to a chat on webpages.
But probably the biggest change in Skype 3.0 is commercial click-to-call. With the help of Google it means a single click on an ad will dial a salesperson at the particular company.
You can download the software now at the Skype website.