Don't bother with iPhoto for editing. Organizing maybe but certainly not editing.
Adobe Photoshop Elements 6 for Mac is only $99 and well well worth that price. Get this book as well.....
I've got a Mac as well and what I'll do is download all the images from the camera to iPhoto. Then I'll go in and move the shots I think are worth a closer look into a album called something like "To PS
". I'll then export all those images as original (RAW) files into a directory on my HD
called "Preprocess". I'll then one by one work on the images in Elements and when I'm done save them to another directory called "Processed"
If I want to send the images to MobileMe or facebook, etc I'll import the edited images from the processed directory into whatever album I want in iPhoto so I can find them easily.
I do it this way because iPhoto's organization is intuitive for me and so it works well for that. It might be a bit repetitive and redundant but, it works for me.
I am also a newb and learning but, I've got a workflow that works for me and that helps a lot.