If you not only enjoy sharing photos but also being able to learn about photography as well, then you may wish to check out Flickr. Flickr is owned by Yahoo and a Yahoo account is required but worth it if you wish to have a Flickr account. As of a year ago, Flickr had over 26 million users.
A free account allows you to only see the last 200 pictures you have posted and you can only post a picture to 10 groups. Groups relate to a topic which can be related to camera gear used, locations, types of photos, etc. You can discuss in these groups not only photography but also topics relevant to the group. If you are travelling, there is probably a group for the places you are visiting that you can check out for pictures posted in the group and even post questions or comments about the area. For $24.94 a year you can get a Pro account. This enables you to have stats on your account, unlimited uploads and storage, ad free browsing and other benefits. No matter what type of account you have, you can tag your photos which enables pictures to be found easier when doing a search by topic.
This is such a popular site for photography that in May of 2009 the official White House photographer Peter Souza started to use Flickr as a way to release White House photos.
If you have even a passing interest in photography this is a site worth checking out. You do not need to have an account to go through the site and check out the pictures and groups. You may decide to stay awhile. Click to see pictures in my Flickr account.