There's a great repository of buttons at gtmcknight.com.
You too can create a custom button for your site with Kalsey's Button Maker.
Here's one for Learning Movable Type:
If you would like to add a Learning MT button and link to your site please host the image on your own server. (You can download it from this page by right-clicking over the image and selecting "Download Image to Disk" or "Save Image As".) After you upload the image to your server you can use this code to add the link to LMT:
<a href="http://www.learningmovabletype.com/"><img src="http://www.your_web_site/path/to/images/button.png"></a>
Note: if all you want is a link to LMT without the image, use this code:
<a href="http://www.learningmovabletype.com/">Learning Movable Type</a>