For a few of my smaller sites (like my portfolio website, www.jeffgeerling.com), I've had a little todo item on my list for the past year or so to make the them 'more responsive'—mostly meaning "make it legible on an iPhone or comparable Android phone". Most tablets I've used render traditional 960px layouts appreciably well, including the iPad, Kindle Fire, Samsung Galaxy Tab, etc., so I want to just focus on making the websites usable on smartphones.
What we had, and what we're going for (which one seems more readable and user-friendly on a small screen?):
I'll show you how I quickly (in less than half an hour) added a
<meta /> tag to the site's
</code> tag to instruct mobile phones on the width of my site, and how I added a simple <code>@media query to my theme's stylesheet to apply a few layout rules to make the design of the site better for mobile phones.