Picasa is a photo organizing program for PC. You can download it here for free. I would first like to say that I am neither an expert on Picasa, nor do I particularly like it, but it's what I use. So here are a few basic tips, I don't use it for much, mostly just for viewing my images, but perhaps other people will add to what I start.
The main reason I liked Picasa when I first started using it was that if you move an image around in your folder system, Picasa will track it and change the location in the program as well. It basically just reflects your folder system. Previous to this I had been using iPhoto on my Mac, which I felt royally screwed up my photos with some crazy folder system that I had to spend a lot of time redoing. I like that this doesn't mess with my folders and just reflects my changes.
When first installing it, there are a couple key options to get right. First go to Tools -> Folder Manager
This will bring up this box where you can select what folders you are viewing images for. So you can use it just to view your digital scrapbooking folder if you want (that's what I do, since I use Lightroom to edit my photos).
Also, go to Tools -> Options. Here you can set what file types Picasa will show you.
Some other quick tips. If you're looking for the tag window, click on this icon:
Also these little icons show you how you view your folder system. You can see I have the one on the right highlighted which personally I like much better.
That's about all I have for now. If you have any questions or advice, feel free to leave it below!
I've been using this program since this summer. I initially got it because it was recommended for scrappers to keep track of things, (I'm a PC user, not apple or mac)
It's face recognition is truly out of this world, at least for the pc user. I got my dad working with it as we both are in charge of family reunions on my mom's side, that occur annually for those that can make it which is usually between 80-130 folks. It's intuitive, and can learn the more you tag someone, and then it will suggest the faces of folks in your photos. This even works well with close relatives, my mom is one of 4 sisters and has 5 brothers, so we really put this feature to the test!
I've started tagging my digital scraps with PU, S4H, S4O, CU, and CU for CU. So that I know what's available depending on how I want to use the items. I've also added designer tags for those that are sharing items and are just starting out and may not have labeled their items well. There are quick tags available as well!
It will also filter by colors without you having to tag things or the color in the file name. Just type in Color: blue and you will see photos of folks were a shade of blue and your digital scrap assets that the program feels are in this color scheme as well.
I didn't realize it could search by color without tagging first. Cool!
Oh thank you thank you thank you
Now i will try to see if i get the hang of it 
Oh, one more thing, at this point...
My dad has already made several of the photo "face" movies, and enjoyed it! Showing them to my grandmother and others. It's a nice feature and we will probably use it some at the reunions.
I use Picasa for looking through my many snapshots and a kvick transfer (rezsized) for the web og original transfer til Elements. Has some good features also - but no possibility to work with layers.
Not sure where it was, but Thanks Marisa for sharing that Picasa has the ability to view psd files! So I use Picasa to find items and then click on the manila folder in the middle panel to open the specific directory folder, so that I can drag and drop files into GIMP. Or I select the file and use the short-cut Ctrl-Enter to locate it on my computer.
This is very helpful, ...now if only GIMP would give us a way to preview those brushes and fonts!