I use Irfanview for (batch) resizing images on Windows personally, but there are other good free apps out there. I downloaded the powertoy to play with, and it seems great for beginners (I've already put it on a few machines here at work for that reason), but lacks more advanced capabilities (which isn't altogether a bad thing).
I also use The Gimp instead of PhotoShop because its "free" (and I can use it on Linux and Windows
).
Maybe a tutorial thread would be a good idea, and people can put tutorials up for various programs they like to use? An example I threw together is below.
ps. I had a quick look at
this website on beginner astrophotography and it seems to be pretty informative (especially the exposure guide for the moon which I wish I had read earlier).