I’ve enabled Twenty Thirteen on my personal blog and done a little bit of customization. Here’s a CSS snippet for adding some contrast to the header text in Twenty Thirteen — helpful if you use one of the colorful default backgrounds:

.site-title a {
	color: #EDEDE8!important;
	text-shadow: -1px -1px 0 #000, 1px -1px 0 #000, -1px 1px 0 #000, 1px 1px 0 #000;
}

.site-description {
	display: inline-block;
	padding: 5px;
	background-color: rgba(255,255,255,0.5);
}

.navbar-fixed .site-title a {
	text-shadow: none;
}

It turns this:

Screen Shot 2013-02-25 at 10.22.38 AM

into this:

Screen Shot 2013-02-25 at 10.22.19 AM