I use Flickr. I have a pro account which costs somethink like $25 a year. The free account how many pictures I could post. I have been pretty happy with it and there are no ads.
I am a fan of Picasa. I like the display size of the photos and the fact that I can choose to make albums public or private. There are no annoying ad windows which pop up to distract from photo viewing. I also enjoy chatting with other photographers from around the world by way of commenting on other photos and receiving comment on my photos. Great fun!
Webshots has gone from mildly annoying to crashing my browser whenever I go to it. We've had a good experience with a paid Flickr account (pro account) for my son's scout troop and I stubbornly stick to hosting my personal shots on my own website using some vanilla (and featureless) HTML.
Both Flickr and Picassa seemed much better to me from a visitor perspective than webshots, even before webshots became unusable.
Anyone have a paid webshots account? I have no browser crash problems (but I don't use Inferior Experience to access the web either) but I do find the ads are now extremely annoying, and in-your-face rude. Since I have 2500 photos with external links (here, RoT, my website, etc.) I'd prefer not to have to move everything. Among the ads is the option to upgrade for $19.99 to a no-ad, higher-res version.
A question I have about these sites would be which is the easiest, most intuitive site to USE?! As you can see by my lack of an avatar,computer use is not my strong point! While my photos pale in comparison to the masterpieces many of you take it would still be fun to post them.
Thanks for the help.