A user stylesheet for Google Mail that hopefully makes the whole thing slightly less terrible.

gmail.css

/* This is a simple user stylesheet for the current version of Google Mail.
   I think it makes Gmail's design slightly less terrible. Use it with your
   favorite user stylesheet plugin or the excellent MailPlane client.

   -- Hendrik Mans <hendrik@mans.de>  */

/* Mails */
tr.zA {
  height: 1.65em;
}

/* Read Mails */
tr.zA.yO {
  color: #999;
  background-color: #f9f9f9
}

/* Unread Mails */
tr.zA.zE {
  color: #444;
}

/* Highlight mails on mouse hover */
tr.zA:hover {
  background-color: #eee;
}

/* Left sidebar */
div.nH.aeN {
  font: 15px/1.35 Arial,sans-serif;
}

/* Links in sidebar */
a.n0, span.CJ { color: #666 !important }