STOP PRESS.
It was nice while it lasted but I suspect it lasted for only a week. I've checked four of the books listed below today (10th May) and all are back to their usual 34% off - my upcoming one wasn't 60% off so is still at the same price as last week.
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I'm just doing a massive check through of the books in my books page to update the prices to May 2008 prices (and reverse the order of the links) and I've so far found three books that are all at 60% off at Amazon US.
Grab them while the price stays this low.
Beginning SharePoint 2007 Administration: Windows SharePoint Services 3 and Microsoft Office SharePoint Server 2007 (Wrox - Göran Husman)
http://www.amazon.com/exec/obidos/tg/detail/-/0470125292/heme0f
$ 15.99
MCTS: Microsoft Office SharePoint Server 2007 Configuration Study Guide (70-630) (Sybex - James Pyles)
http://www.amazon.com/exec/obidos/ASIN/0470226633/heme0f
$ 19.99
Professional SharePoint 2007 Development (Wrox - John Holliday, John Alexander, Jeff Julian, Eli Robillard, Brendon Schwartz, Matt Ranlett, Dan Attis, Tom Rizzo)
$ 19.99
There are probably more but those are the ones I've noticed so far.
P.S. Another 60% one - this one I might even buy myself (to be fair to the other three I already have two of them).
Mastering Windows SharePoint Services 3.0 (Sybex - C. A. Callahan)
http://www.amazon.com/exec/obidos/ASIN/0470127287/heme0f
$ 19.99
P.P.S. I'm still (this is about 2 hours later than the P.S.) working my way through the books and I've come to the RealWorld one I wrote a chapter for AND they are selling that at 60% off as well. I don't know whether to be offended or not :) ?
Real World SharePoint 2007: Indispensable Experiences From 16 MOSS and WSS MVPs (Wrox - Editor: Scot Hillier. Authors: 16 MVPs
http://www.amazon.com/exec/obidos/ASIN/0470168358/heme0f
$ 19.99
P.P.P.S. I did order the Mastering SharePoint book. I thought I'd need to order some more books to make an order from the US to Finland worthwhile but as I'd just ordered a few books a few days earlier (typical!), I decided to see how much they'd charge for just one book. For $27 and change I will get it here in about 2-3 weeks. Not bad.
(I've also amended the price of Göran's book. I vaguely wondered at the time how that could be the same price as the other ones if it too was 60% off. It turns out it wasn't $19.99 at all but a mere $15.99).
.... and a massive thanks to the first person to order *my* book (via my links that is, but it's still the only pre-order I know about). What a feeling especially as I have just handed in the final chapters!