If you want to show your latest posts on standard-sized banners, then here's a perfect tutorial for you. Once you complete the steps of this tutorial, you will get some animated .GIF images, which are dynamically updated from Feedburner's servers and show latest posts of your blog, like these:
Instructions to follow:
1. Log in to Feedburner.com (using your Google account)
2. Select your Blog (Blog's feed)
3. Then select Publicize tab
4. Now click on "Create new..." link below "Headline Animator".
5. Now create and save the animated banner. Click on "Activate" button and copy the code.