After I used SmugMug for 2-3 years, I switched to Flickr, which I have used ever since. My wife, a photographer, also uses both Flickr and www.photo.net
(a more professional oriented photography site).
Nothing wrong with SmugMug (and their customer service has always been incredibly fast and personal), but whenever I would try to view a photo album, either mine or someone else's, on SmugMug, there always seemed to be a significant lag in loading almost every picture, which made viewing an album on that photo site an unduly lengthy experience. If you view the same photo album using the same computer, etc., but on Flickr, it can be viewed much more quickly, and without the loading time lag between pictures.
I think there were some virus issues in the past using Webshots that, in the case of my office, caused them to block Webshots, but not SmugMug or Flickr, which I have no problem viewing at my office.
I have no experience using Picasa for my own pictures, but my experience viewing someone else's photo albums on Picasa has always been very positive, with fast viewing times and an eye-pleasing, and user-friendly interface.
With any of these, it's worth it to get the basic paid membership. In the case of online photo albums, the old saying that "you don't get something for nothing" is especially true!
And as mentioned above, if you want to post videos, Flickr really isn't suited for that. Laura uses Vimeo, and of course, there is always YouTube.