To set up the MyBlogLog widget just cruise to ‘Sidebar Widgets’ under ‘Presentation’ and drag and drop.
To embed a Slideshare slide just copy it’s wordpress.com embed ID… replace with spaces the ‘id=’, ‘&doc=’ and delete the &w=425. More info on that here.
Update: You can now just copy and paste the code they provide for WordPress.com, i.e.
Thanks to Ring Of Blogs for the fix.