Post update
Jan, 20, 2011
It is now possible to add a Facebook Likebox that is visible right in a wordpress.com blog.
Learn the new trick…
How to add a Facebook Likebox in a wordpress.com blog – part 2
This post assumes that you have already created your Likebox and now you are trying to figure out a way to post it in your wordpress.com blog.
This post also assumes that you use Firefox.
When you create a Like box you will be able to see it in the right side of the page.
Download this nifty little Firefox extension – Fireshot.
Now press ctrl+alt+z in your keyboard.
This keyboard shortcut will use Fireshot to create a screenshot of the whole page. Now carefully crop only the portion of the Likebox. Save the image and upload it in a new post. Now get the link of your blog’s Facebook page and link the image to that url.
Save this post as draft for future reference.
Copy the whole code from the HTML editor. Go to your blog’s widgets page and add an unused text widget.
Paste the code in the text widget and save changes.
View your blog. If you did everything as per the instructions, you should see the image of Facebook Likebox in your sidebar. Since it is linked to the Facebook page of your blog, the reader who clicks the image will go there and from there (s)he can “like” it.
If the image is too big for your side bar, you can put the image in a box with scrollbox to save screen space.
There’s no way to have updated info in this method. To have updated info, you must change the image from time to time.
This is only a workaround for wordpress.com. It’s not possible to make it work completely the way it is supposed to work, because of limitations imposed on us by wordpress.com about what kind of code we can put in our blogs.
Another alternate way
Just use a text link or an image link that links to your Fan page. Then you don’t have to update the information again and again.
See this image I spotted at Dornob. It’s plain, simple and makes its point.
Always remember, the side bar is an important space in your blog. I am not sure that the Facebook Likebox is one of the most important things to allot so much space for! 
Related posts:
How to add both “Share on Facebook” and “Facebook like” buttons easily in a wordpress.com blog post
How to add a “Share on Facebook” button in a wordpress.com blog post in ONE click
How to add the Facebook Like feature in a wordpress.com blog post in ONE click
How to use the Facebook Recommendations plugin in wordpress.com
