I noticed that there is no option to upload .zip files to wordpress.com. Lots of blog services give permission to their users for this. I'm a programmer and a lot of my blogs contain code samples. How can I attach my codes to my blogs?
You can use a free account at http://box.net or Ubuntu One to upload and share .zip files, but unless you have a LOT of code that you want to share, you're probably better off embedding your code samples into your posts.
Wordpress now supports posting source code on blogs hosted through their site:
While WordPress.com doesn’t allow you to use potentially dangerous code on your blog, there is a way to post source code for viewing. We have created a shortcode you can wrap around source code that preserves its formatting and even provides syntax highlighting for certain languages [...]