Who can use Flickr

Anyone is free to join Flickr , you just need a yahoo user id. If you do not have one then you can get one here

Pro Account for just US$24.95 a year, you get:
Unlimited photo uploads (20MB per photo)
Unlimited video uploads (90 seconds max)
Unlimited storage
Unlimited bandwidth
Unlimited photosets
Archiving of high-resolution original images
The ability to replace a photo
Post any of your photos or videos in up to 60 group pools
Ad-free browsing and sharing
View count and referrer statistics

With a Free Account, you get:
100 MB monthly upload limit (10MB per photo)
3 sets
Photostream views limited to the 200 most recent images
Post any of your photos in up to 10 group pools
Only smaller (resized) images accessible (though the originals are saved in case you upgrade later)

Getting Started with Flickr
There is a great help section on the Flickr website if you need any specific assistance with using the online tools, uploading photos etc .
A tutorial (of sorts) about some possible ways that flickr may be useful in the classroom can be found in the notes attached to a photo on my flickr site