If you are running Athena RTM, then open up ~/Themes/Athena/Athena.xml
<dropdowns>
<dropdown name="blog" type="blogs">
<link name="listings" appkey="cslistings" mode="remove" />
<link name="nickblog" appkey="nickblog" mode="change" navigateurl="http://www.techienick.com" />
<link name="showcase" appkey="showcase" mode="change" navigateurl="http://showcase.nbdev.co.uk" />
</dropdown>
</dropdowns>
That's fom my website. It shows that you can remove links, and change others.
It also supports urlformat="~/ThemeShop/##Subject##/Default.aspx" where ##Subject## would be the subject of the post or ##PostId## where postid is the id of the post.
YOu can also add a new drop down menu
<dropdown name="info" type="custom">
<link name="about" navigateurl="~/info/about.aspx" text="About" mode="add" />
<link name="contact" navigateurl="~/info/contact.aspx" text="Contact" mode="add" />
<link name="services" navigateurl="~/info/services.aspx" text="Services" mode="add" />
</dropdown>
Hope this helps