I want to put 100 issues (64pp each) of a paper magazine onto a DVD,
with browsing and searching capabilities. What kind of vendor or
technology could help me with this? Examples include "The Complete New
Yorker", 4000+ issues of The New Yorker on seven DVDs, as well as Mad
Magazine (a CD-ROM set which came out in 1999, I believe) and National
Geographic.

you could convert the pages into pdf's
u could use something like http://www.gxo.com/download.php
or for something a lot more serious i would suggest
http://www.adobe.com/products/acrobatpro/main.html
acrobatpro is what most companies use.. 
hope this helps..

Unfortunately, the simple PDF-based solution does not address the
browsability and searchability features I have in mind.

well with pdf its all down on how well its composed.. 
since u can add searches into it.. 

well it depends on what sort of criteria people will be searching on.
since if its something with mass amount of searches you could make a
in eg html, php etc..

You may have to use OCR software on the scans to be able to get text
for these programs to work.

I would recommend that you use one of the many excellent
Javascript-based search engines normally used for indexing and searching
a web site. Many of them now have support for WordPerfect, Word, PDF,
and Excel file formats and can create indexes for CDs and DVDs. They
provide many of the advanced features that people are used to when
searching on the web and provide the same user-friendly interface as
web-based search engines do in any modern web browser.

As examples, I would recommend either Zoom
(http://www.wrensoft.com/zoom/) and the necessary  Zoom plugins (with
Javascript option) or Atrise Everyfind
(http://www.atrise.com/everyfind/). For Zoom, the standard version will
run you $49 (and is limited to 100 files) or $99 for the professional
version. Atrise Commercial Project Edition will run you $120. With both,
you get royalty free distribution of the searches on your CD-ROM.

Screenshots are available on the product's sites.

With all due respect, I would encourage you to re-investigate PDFs. I
say that because your objection to their lacking adequate browsing and
searching capabilities indicates you might not be familiar with all
the possibilities. Acrobat 7 added some wonderful functionality,
including integrated OCR.

I have implemented, administered and used high-end commercial document
management systems. Unless you require a complex database to index
every page a thousand different ways, Acrobat is a fabulous interface
if the documents are set up correctly on the front end, and it is also
a good tool for the initial document setup.

I agree with awpaultech.  I've scanned thousands of pages of documents
using adobe acrobat.  They have a feature called paper capture.  This
scans the document and identifies each word.  After this scanning is
complete you can then search the document, or all the documents using
any word or phrase you're looking for.  One big problem... If the
documents you are scanning are not close to perfect - good black text
on a white background - just like you are reading here - then some
words are not read correctly in the capture process. Faded newspaper
text on a low contrasting background gives me lots of problems.

I would look into a company that does microforms. They have the
equipment to photograph each page and put it on a strip of film, that
can hold several thousand pages. I would imagine that they would have
extra features that would allow OCR to make it searchable and possible
to put those images on DVD too.

I've found a company in India that appears able to handle this well,
using graphic page images with "hidden" text underneath that is
searchable:

http://www.suntecindia.com/data-entry-india/pdf-image-searchable-text-conversion.htm