Found this morning via Versiontracker, BrT » CopperExport is a plugin for iPhoto 4 or 5 which exports to Coppermine Gallery 1.3 or 1.4 beta.

Great idea, could have used it when I was hosting my own pix 🙂

Requirements (as per the website): Mac OS X 10.3 Panther and iPhoto 4.x or 5.x. iPhoto 2.x may work, but has not been tested. Versions of Mac OS X prior to 10.3 will certainly not work.

Seems like there might be issues with Tiger of varying kinds, when looking over the comments. Its been generally well received though.