Wired Wiki has a nice writeup of how to maximise your Flickr usage. They've thrown in some basic tips as well as a number of alternative apps or plugins for customising tasks like uploading photos. Nice to see them offering some Linux alternatives and Python gets a mention too.
It also rounds up some tools for uploading pictures to Flickr using mobile devices and email:
"Not many people know this, but you can also use Google's free Picasa application to send photos to Flickr via GMail. As of version 2.0, you can e-mail directly to Flickr from the Picasa app, which will even automatically resize your photos before sending them. Just use the aforementioned Flickr e-mail address and send your pics from GMail."
If you're a dinosaur like me who's still using Photobucket, this might kick you along to try out Flickr. :)