Hi Diana. PDtax here.
Since ranking Justices by leaning is subjective, I wanted to start with rankings that are readily available. Start with one found at http://wiki.answers.com/Q/Who_are_the_US_Supreme_Court_Justices_in_order_from_most_liberal_to_most_conservative#slide1
and follow the slides. This author listed Ruth Ginsberg most liberal, to Alito, Roberts, Scalia and Thomas, considered the most conservative. The other four Justices are somewhere in the middle.
http://www.vaughns-1-pagers.com/politics/us-supreme-court-summary.htm offers a similar rating, along with some pretty extreme political rankings and views. I'll re-read this in the morning after a coffee or two.
There are a number of sources, but the listings are generally consistent throughout. http://en.wikipedia.org/wiki/Segal–Cover_score lists this rating scale for Justices political leanings. The current members are listed at #37-45 on their list.
Hope this helps. Thanks from Just Answer.