If you're blogging on wordpress then this plugin is worth a look:
http://wordpress.org/extend/plugins/post-snippets/
Use it for bits of code that you use repetitively throughout your blog posts. You don't have to keep typing out or copy/pasting that bit of code in every post, just click the button in the post editor. And if you want to change a code snippet, you edit it once and it updates it everywhere it appears on your blog.
For example, let's say you use it to place banners on your blog posts. You write 20 blog posts that include a particular banner and then the sponsor decides to kill the site, leaving you with 20 dead links. Simply update the snippet code, and now all 20 banners are updated.