Here is a SASS file that will help with theming your Wordpress Login page.

gistfile1.scss

@import "compass";

body.login  {
    // background: transparent url(../img/bg-footer.png) 0 0 repeat;
	h1 {
		text-align: center;
		a {
			width: 320px;
			height: 92px;
			// background: url(../img/logo-login.png) 0 0 no-repeat;
			background-size: auto;
			text-indent: -9999px;
			overflow: hidden;
			margin: 0 auto 15px;
			padding: 0;
			display: block; 
		}
	}
	form {
		margin-left: 8px;
		padding: 26px 24px 46px;
		font-weight: normal;
		background: white;
		border: 1px solid #E5E5E5;
		@include border-radius(3px);
		@include box-shadow(none);
		.input {
			font-family: "HelveticaNeue-Light","Helvetica Neue Light","Helvetica Neue",sans-serif;
			font-weight: 200;
			font-size: 24px;
			width: 97%;
			padding: 3px;
			margin-top: 2px;
			margin-right: 6px;
			margin-bottom: 16px;
			border: 1px solid #E5E5E5;
			background: #FBFBFB;
			outline: none;
			@include box-shadow(rgba(200, 200, 200, 0.2) 1px 1px 2px inset);
		}
	}
}

//Set your two colors for the button
$main-blue: #008fb1;
$dark-blue: #077b97;

//Overwrite the default Blue WP Login button
#wp-submit {
	background-color: $main-blue;
	@include background-image(linear-gradient($main-blue, $dark-blue));
	border: 1px solid $dark-blue;
	border-bottom: 1px solid darken($dark-blue, 5%);
	@include border-radius(4px);
	@include box-shadow(inset 0 1px 0 0 lighten($dark-blue, 40%));
	color: #fff;
	font: bold 11px/1 "Lucida Grande", "Lucida Sans Unicode", "Lucida Sans", Geneva, Verdana, sans-serif;
	padding: 7px 0 8px 0;
	text-align: center;
	text-shadow: 0 -1px 0 darken($main-blue, 10%);
	width: 40%;
		&:hover {
			background-color: darken($main-blue, 2%);
			@include background-image(linear-gradient(darken($main-blue, 2%), darken($dark-blue, 2%)));
			@include box-shadow(inset 0 1px 0 0 lighten($dark-blue, 20%));
			cursor: pointer;
		}
		&:active {
			border: 1px solid #5b992b;
			border-bottom: 1px solid #538c27;
			@include box-shadow(inset 0 0 8px 4px darken($main-blue, 10%), 0 1px 0 0 #eee);
		}
}