iPhoto has absolutely everything you could wish for from a photo app, including Geo-tagging and Facial Recognition, but one thing that's been lacking for a while is support for exporting to Flickr.
No prizes for guessing what FlickrExport does then. FlickrExport is a plug-in for iPhoto, which provides a direct export interface to Flickr, enabling you to upload your images in double-quick time. You can create photosets with your uploaded images, add your photos to multiple groups after uploading, and it retains Geotagging data as defined by iPhoto.
The result of using FlickrExport is that your photo stream will be much easier to keep updated. You can, of course, edit photo titles and descriptions, add tags to them and even send your photos to a group pool. The only drawback is that after an initial periods of being freeware, FlickrExport is no longer free to use. But if you're a Flickr/iPhoto user, you can't go wrong.
FlickrExport is an extremely useful - nay essential - add-on for any iPhoto user that has a Flickr account that they update regularly.