I’ve just read a recent post on the WordPress.com blog which shows you have to display source code within your blog post (for WordPress.com users, but also available as a plug-in for wordpress.org users).
It is very easy to use and presents the code clear and readable. Support is available for a number of different languages and there are are number of presentation options as well.
I’ve updated a number of my old posts to support this. Check out: Using SQL to loop through a result set as an example or search using the ‘sql’ tag.