<a href="http://www.psd2cssonline.com/" rel="nofollow">http://www.psd2cssonline.com/</a> attempts to automate the process but you need to lay out the PSD in a certain way.
I use and recommend <a href="http://www.psdahtml.com" rel="nofollow">http://www.psdahtml.com</a>, not the cheapest one but very serious about delivery dates.