Here are a few ideas., since you asked (I think?)

Stefano Mazzocchi:

Creator or Cocoon, one of the people behind the Simile project, now at
MetaWeb ... I think Stefano's experience with public speaking, open
source software, data processing and the web would make him a
compelling keynote.

Andy Powell:

Long time metadata wrangler, and moving force behind organizations
like UKOLN, JISC, Open Archive Initiative, Eduserv. Andy's been a
strong advocate for the use of web technologies, and web architecture
in the digital library space.

Ian Davis:

CTO of Talis, architect of their RESTful semweb platform, co-author of
RSS 1.0, creator of FRBR RDF vocabulary, articulate and experienced
speaker on the use of the web and semantic web technologies,
particularly (but limited to) the library space.

Tim Spalding:

The guy behind LibraryThing. His insights into the communities around
books and libraries, and how to enable them on the web are fun,
invigorating and inspiring.

Carl Malamud:

Long time advocate for Internet technologies for the public good. Most
recently involved with making public domain data sets available to the
public w/

Jon Orwant:

Perl hacker, author, former CTO of O'Reilly, now at Google Book
Search. Would be fun to hear where he thinks libraries and books, and
hopefully he'd throw a mug or two.