Auction Catalogs - A Last Minute Christmas Suggestion
The major auction houses all produce catalogs of their key auctions held throughout the year and most offer subscription packages. In comparison to a magazine subscription, they're a little steep, of course, but auctions provide a unique way to get an overview of photography in all its different forms, at least based on the contents of most recent auctions (though you might get more than you're fill of Helmut Newton.) The downside is that they can appear a little bit like a grab bag with little curatorial direction unless an auction represents the prerogatives of a single collector. Still, they're a unique photo gift you might want to consider.
Christie's
All locations, $167, approx. 6 sales/year
New York only, $90, approx. 3 sales/year
London only, $68, approx. 3 sales/year
Sotheby's
4 issues per year, $125
Covers both NY and London auctions (2 catalogs apiece); location specific catalogs, 2 issues, $80
Phillips dePury & Co.
2 issues per year, $90
Swann Galleries
No catalog subscriptions, individual catalogs are $15-$35
Bonhams and Butterfields
Subscriptions are not offered online. For more information, send an email to "info@ butterfields.com".

Hey, Great Blog!!
I think both the Photography and the Contemporary Art Auction catalogs are a great resource to see a survey of the market.
But if you just want them for the info, you're much better off buying them at The Strand Book Store where they typically sell for just $3 to $5.
Also they sometimes show up on EBAY.