A few good sites that have always helped me for a quick reference, or some tricks/tips are these:
(These should all pop up somewhere In the first page of a google search)
http://www.w3schools.com/css/default.asp
http://www.echoecho.com/css.htm
http://blog.outer-court.com/archive/2007-03-30-n51.html
http://www.csstutorial.net/
Also, if you see a site that looks good to you, just look at their CSS. If you do a "View Source" you will usually find a line of code that says
Code:
<link href="[FILENAME].css" rel="stylesheet" type="text/css">
And go to wherever the file is. (usually in the same directory)
Anything within those sheets will usually give you a few ideas as to how to get something done. That is one thing that is cool about CSS it is pretty straightforward (ie. Background, color, font-family, etc..)