Having used Flickr for over 2 years, I think it is a great way to network with other people who share a passion for photography. The search functions are easy to use and cover everything under the earth and even some times above it. This makes it a very useful resource for presentations.
One of my Grandmother's Photo's from her Flickr Account:
Picnik is the editing program of Flickr. It is very easy to use and allow for a variety of edits even on a free account. As with most things, more can be achieved if you part with money to upgrade to a pro account. Editing a image can be as simple as putting some writing on it or cropping the photo, to changing the lighting effects and colours of the photo.
In the following photos from my recent trip to Hong Kong and the Fishing Village Tai-O, I have cropped the photo as well as sharping the image and changing the lighting to make the whole image clearer. I have also added text showing the place and rough time of the photo.
Before (Top) - After (Bottom)