I do not understand how companies can give away software and still generate revenue. Economics was never a strong suit for me. Nonetheless, I enjoy this free software phenomenon, and there's a couple I'd like to point you to.
Google purchased Picasa, hoping to boost it's blogging service, and is now offering their latest version of Picasa for free. It's a pretty sweet application suite, and the intergration with Blogger.com is good, too, although I've not decided whether I'm going to switch over.
And if you want a photo and slideshow program, try Microsoft Photostory 3. I haven't used this as much, but just about everything I've heard says it is worth the download.