How Do I Register a Group of Published Photos?

we can send a man to the moon, but ...

Dear Rich: I’m mystified by the copyright registration rules. I post daily photos on a photoblog, and though there’s no explicit offer to sell them, I mention that I’m represented by an art gallery. I’ve been filing about 100 images every three to four months as unpublished photos, but now I worry that those filings may be defective because they may technically be published. Is there any way to go back and fix the filings if they’re improperly filed? And going forward, is there a way to file a large batch of published images all at once? I certainly can’t afford (money or time-wise) to register 300 to 500 individual images every year.
We sympathize with your plight. You're wrestling with three confusing copyright issues:
Is a photo published when posted online?  Although courts and legal experts have debated the issue over the years, it appears settled that posting photos on the Internet in a manner in which they can be copied or downloaded (and restrictions are not imposed), constitutes "publication" under copyright law.
Is there a way to go back and fix filings? The Copyright Office provides Form CA for use when the facts in an earlier registration are incorrect or incomplete and you want to place the correct or complete facts on record. Before making that correction, we would suggest you speak with an information specialist at the Copyright Office. Call (202) 707-5959 or 1-877-476-0778 and press "0." (Here's more on the procedure.) Inquire as to whether a correction is necessary in your situation.
Is there a way to file a large batch of published images at once? Yes, we discuss it in this video and the Copyright Office explains the rules here and here and explains the eCO filing method, too. Of course, if you prefer registering the works as unpublished photos simply file your application as an unpublished collection before you post your photos.