Picasa is cool. Like Scrapble said, you can tag people in it, which is awesome.
Other cool photo organization programs are Adobe Bridge (which comes with Photoshop) and the Adobe Photoshop Elements Organizer (which comes with Photoshop Elements).
My personal favorite, and I can rave about it for hours if you let me, is Adobe Photoshop Lightroom. Once installed, you can set it up to automatically open & bring up import files box when you stick your camera's memory card in your computer. It will automatically copy the photos into the right spot on your hard drive, and all of the settings are customizable.
My Lightroom is set up to save the files in a folder for every year, and sub-folders for every day. For example, my Christmas photos went in My Photos/2012/December 25. So, in effect, the photos get organized by event. You can set up Lightroom to automatically tag events if you keep on top of things and import photos after every event, and put other kinds of metadata into the files. The newest version of Lightroom has geo-tagging support and you can find photos later by location (if you import your photos from a camera phone or something with geo-tagging in it).
Then you can non-destructively color-correct photos, crop them, and do spot removal. And you can export them formatted for the web right there, without ever having to go into Photoshop.
By the time I get into Photoshop to scrapbook, my photos are ready and I can concentrate on making my page.
I usually organize my digi kits in Bridge, and organize my photos in Lightroom. It works for me

One more thing about Lightroom: the new version has a Photobook option. I haven't done it yet, but I've heard about it and have been meaning to try it. It will let you arrange your photo book right inside Lightroom, and will even automatically upload it to Blurb for printing. Next time I print a book, that's what I'm doing

Online, for sharing photos, I like the Shutterfly share sites and Photoshop.com. But I haven't done any big family photo sharing online in a while.
Mary