[Flickr APIs] Getting started - list photos in Flickr

Hi folks,

I'm trying to get started with the Flickr APIs.  The first thing I'd 
like to do is simply get a list of the photos belonging to a user, using 
their authentication credentials.

But I'm having a bit of a problem.  The only method I can see that 
returns a list of photos is photos.search, which takes a user_id 
parameter to filter by user.  However, I don't see a way to get the 
user_id for a user, given their login credentials.  What am I missing?

Thanks,

Abe Fettig
http://fettig.net/