What theme is good for posting code?

I would suggest that you flip the question to What plugin is good for posting code?. You can only do so much with <pre> and <code> HTML tags. I post code snippets on my blog all the time using the WP-Syntax plugin. Here's a nice working example:

A WordPress Blog Post with PHP, TXT and HTML snippets using the WP-Syntax Plugin

It allows me to identify the code I post as CSS, HTML, JavaScript, PHP, plain text, and many more. Then it color codes the snippets accordingly.

It also preserves indents which I've found very useful for usability/user experience when copy/pasting decent sized code snippets from other sites.

The syntax is easy, you just switch to the HTML editor in a post and wrap all of your code in a <pre> tag. For example:

<pre lang="php">
  <?php
    echo "I love cheese!";
  ?>
</pre>

The above will output a nice color coded PHP snippet. The plugin leverages the GeSHi syntax highlighting class to do its dirty work. All of the available languages are outlined on the GeSHi website.

In the end I used the theme called Elegant Grunge from Michael Tyson.

I'm using Windows Live Writer 2011 with the Insert Code plugins for it, and it works very well.

Check out my blog Alphaot.com to see how it ended up.

Perishable Press has extensive tutorial on styling <pre> tags, including nifty auto-expand on hover for long lines.

I personally find the CSS method to be suitable..

https://stackoverflow.com/questions/322929/word-wrap-in-css-js

See the answer provided by Jake Scott.

I've found success using Nathan Rice's Single Post Template plugin, and creating a "no-sidebar" template page for posting code. Works pretty well for most cases.