Groups are the standard way, but require more maintenance. Plus, group pools often get bombarded by "group whores"*
Photos that are marked "private," should not be added to the RSS (and you don't want people randomly browsing these, right? So you should be marking them private anyway)
I have a few robots set up -- originally to "compartamentalize" my own contacts lists -- a lot of people have found them useful (including a few flickr & Yahoo employees, so I'm not too worried about the fact that they appear to be, technically, a violation of the Yahoo TOS -- but doggone it, they were there before Yahoo bought flickr!
)
KB
* A "group whore" is someone who massively cross-posts every picture they have into every group they can find just for the sake of coverage. They rarely, if ever, participate in those groups, and the material they post is often 100% inappropriate for the group pool -- in APUG's case, the criteria would be pretty obvious.
In "New Black and White," which I attempt to moderate, in the past eight hours of Sunday morning the group has received over 50 submissions from cross-posters, most of which I will delete. The same posters will continue to blindly bombard, because frankly they're just spammers. They cant however, spam the robot since they need to have been selected as a contact before.
(Oh, and if a group is private, it doesn't publish an RSS feed)