Looking for some advise on training materials

I want to get some folks some professional development work to do on
the topic of databases (PostgreSQL-related, but I'm looking for
some more general material on the subject of relational design, etc as
well)

Because the training budget is used up for this year, and I don't want
to wait until January, I'm trying to find things that are inexpensive
enough to get started on right away.

To that end, does anyone have any recommendations?  Something like a
self-guided online course, or a book that's written specifically to be
a self-study?

--
Bill Moran <wmoran@potentialtech.com>