RE the posts on the ND grad filter effects available in CS4 Adobe Camera Raw, the same tool is in Adobe Lightroom, which also uses ACR. It is a very useful feature. For a tutorial on it have a look here:
Workshops-On-Demand
It is about three minutes into the tutorial.
I think the entire set of Lightroom tutorials are very worthwhile. If you were going to download the 30 day trial of Lightroom I would highly recommend looking at the tutorials before starting the 30 day clock ticking.
I attended a day seminar put on by JuliAnne Kost on Photoshop and she is simply excellent.