Disclaimer: I'm the founder, CEO & Chief Geek at SmugMug, a popular photo sharing site.

The good news is that there are lots of great sites out there, and they serve lots of different use cases. The great thing about the Internet is that there's a site for everyone. :)

Here are a few of my favorites:

• Facebook is by far the largest, and certainly the easiest answer for your specific question - sharing with your friends and family - because they're probably already there and they'll just see your photos in their News Feed. The downside is that for this audience, the resolution is low (4Mpix max), and the display and interface will likely leave you wanting more (though their new lightbox is nice).

• Flickr is a great site for people looking for higher quality than Facebook and a high level of social interaction and critiques. It supports higher resolutions than Facebook, and while it doesn't have nearly the enormous user base, there are still many millions of very active users who love to comment on your stuff. The user interface is designed around that social interaction, though, so if you're looking for a site that focuses more on the display of your photos, big and beautiful, Flickr might not be your best choice. Navigating from photo to photo is particularly painful, in my opinion, but leaving comments and getting feedback is a breeze.

• SmugMug (the site I run) emphasizes the display, rather than the social interaction with strangers on the net. At SmugMug, your photos are shown big and beautiful, using all the available pixels. Sharing via email or on sites like Facebook and Twitter is easy, but you do have to do a little more work than you would at Flickr (and a lot more work than at Facebook) to let your friends know where to find your photos. With more than a billion photos and tens of millions of users every month, SmugMug isn't nearly as large as Facebook (30B photos, 500M users) or Flickr (5B photos), but it's not small, either. The other large gotcha with SmugMug is that it's a premium site - every customer pays - while Flickr and Facebook are free.

There are plenty of other sites out there that address other aspects of photo sharing (like printing, or twitter-specific hosting, etc), but these three probably cover the question you asked best. Now it comes down to what your preferred sharing style is - very social or high quality or something in between?

One last important note, both Flickr and SmugMug integrate well with Facebook, so this doesn't have to be a "choose one" choice.