I had a great time exploring Flickr. I was amazed to see how many ways there are to get your photoa online - you can even snap photos on your phone and email them to Flickr. Sets/Collections is another great feature, and there aways you use this feature on large batches, and do thins like tagging, changing permissions and setting editing limitations. All-important privacy settings are also available.
The mapping feature was very interesting, but what I am most excited about are the photo book capabilities. Knowing that this is available has gotten me to get out my digital camera and really start taking some pictures.
Another wonder find was the section on the "most interesting photos". These images are awesome.
All in all Flicker is great place for photo ideas, especially for a photography newbie like me - helping me to come up with ideas for my own projects.
To try the tagging feature I explored beach photos, and the search resulted in tons of gorgeous images. The picture at the top of this post is an example.