From iForgot Systems:
Free Flickr eXporter iPhoto Plugin (FFXporter) is an iPhoto export plugin for Flickr. This provides a convenient way to upload descriptions, titles, keywords (tags), and ratings along with your photos. It also supports sets (yay!). Flickr is a free photo sharing service/site.
What's new in this version:
Brings compatibility to Mac OS X 10.8 and iPhoto '11
More robust uploads
Updated update framework
Yes, this is actually getting updates after 4 years