It is easy to display photos on your website without using any software and without having to worry about storage. The Flickr badge generator is one tool that we like and see a lot of organizations using. Once you upload your photos to Flickr, you can tag them and organize them into sets. Based on your tags or sets, you can then selectively choose to show photos. For example, once we uploaded photos from the past several NTEN Nonprofit Technology Conferences (NTC), we were able to produce this badge in about 5 minutes choosing the photos we have tagged with "NTEN":
After generating the badge on Flickr, you can choose to display it as HTML (above), or Flash (below). Flickr's badge generator provides you the code to embed in your website.