When at the IOD Conference, I had the pleasure of meeting two people who are experts in the mashup area: Bobbi Cochrane and Ginny Ghezzo. On both occasions we randomly met while eating breakfast... and ended up talking about mashups with all the people sitting at the table.
Bobbi gave me a card that introduced the IBM Mashup Center which is an enterprise mashup platform to unlock data, remix content, and unleash productivity. Give it a try on greenhouse.lotus.com.
Also at the conference I met the publishers from Wiley who publish the Dummies series of books. They mentioned that they are interested in new titles including one on mashups. That brings me to mashup experts in Haifa: Ohad Greenshpan and Aya Soffer who have written several articles on the topic... and may make excellent authors of a book.
The IBM Database Magazine that came out today introduced me to the Mashup Camp which looks very interesting. The website calls it The Unconference for the Uncomputer. This issue also has a link to the a podcast of Curt Cotner speaking about mashups.
So far I can only find two books on amazon about mashups: Pro Web 2.0 Mashups: Remixing Data and Web Services (Expert's Voice in Web Development) by Raymond Yee. There are 4 reader comments on amazon, all positive, but let me know if you've read the book and if you recommend it. It published in February this year, so it is fairly recent.
A search on developerWorks brings up 359 matches on the keyword mashups.... so, you'll be able to find many articles if you search, including this one: Choosing between mashups and traditional Web applications - Considerations for leveraging IBM Mashup Center.
I'm looking forward to learning more about this area and hope you are as well.