Linux: The default image scanning app on most Linux desktops, XSane, has many, many buttons and sliders. When all you want to do is make a PDF from text, or scan a picture, Simple Scan is there for you.
Robert Ancell, a developer for Ubuntu backer Canonical, is developing Simple Scan to drop into the next release of Ubuntu, Lucid Lynx, due out in April. Although his software isn't officially at a finished, 1.0 stage, it's already decent enough to be an attractive install for Ubuntu users. Load up your scanner, plug it into your system, fire up Simple Scan, switch between Photo and Text, and hit the Scan button. Yes, you can adjust the dpi resolution, create multi-page PDFs, and crop your results, but you usually don't need to. The buttons to save, email and print your results are all there, too, and this app just works.
Simple Scan is a free download for Linux systems only. Source code is available in addition to Ubuntu packages, but we're guessing the app runs best on Ubuntu.