RGB80 is useful website which allows you to search Flickr photos by the tags. Flickr has a vast collection of photos and RGB80 simplifies searching these photos using tags. This website offers good tools to search photos, sort by date and relevance of photos. It also shows the popular searches for tags in Flickr. The search result shows Flickr photos in thumbnail mode and also paginated.
In the search result, you can see the sort options which are by date, by interesting and also by relevance. Clicking the photo opens it in pop up mode which shows it in bigger size (same size as that of Flickr).
Hovering on the info link will show the photo title and date taken if available. There is also a link to the original Flickr photo. Apart from the popular search tags, the site also shows related tags in a tag cloud to the actual search.
Overall RGB80 is a good service to search Flickr Photos by tags and also preview them without actually going to Flickr.