Acutally, it gets even easier in PhotoShop6. You can assign your saved sequence to a batch of files. You then have the option of replacing the original files with the newly converted (always a bad idea...why they even give you the choice is beyond me), or save the new files to someplace you specify.

I do this all the time for a friend of mine that has an online photo gallery. It is very simple and totally automated. The only drawback is the price of PhotoShop. Corel PhotoPaint can do the EXACT same thing for half the price. And Corel is becoming a clone of Adobe now (evern since v9). They heven have an Adobe interface emulator!