I shamelessly copied the following CSS from [Oliver Boermans](http://www.ollicle.com) who uses this in one of his [NetNewsWire][nnw] themes.
I like it mostly for the overflow, but it does set code off by itself.
I hope that Matt adds it to the default themes in [Squib][]. Subtle hint.

    pre {
	  background-color: #f9f9f9;
	  border: solid 1px #ccd;
	  padding: .5em .75em;
	  margin: .4em 0 .4em 0;
	  width: 100%;
	  overflow: auto;
	  }
    code {
	  line-height: 1.2;
	  color: #336;
	  margin: 0 0 0 0;
	  padding: 0.1em 0 0.1em 0;
	  }

[nnw]: http://www.newsgator.com/NGOLProduct.aspx?ProdID=NetNewsWire
[squib]: http://squib.rubyforge.org/