What can you tell me about poster design and typography in LaTeX?

beamerposter is a beamer-style poster/canvas "utility". Features include posters in A-series sizes, and custom sizes like double A0 are possible.

Some great examples are available from the beamerposter online resource.

There are some pointers as to the typography in Conference Announcement Poster. However, just to add my two cents, I personally feel that this type of design as well as book covers belong to a professional graphic designer. Let someone with a more artistic background do the design and you can do the easy part which is the Texing. As other answers mentioned this can be done through beamerposter, a0poste, sciposter, baposter or you can produce your own set of macros, if need be.

Most good graphic design books (rather than typography books) spent an inordinate amount of write up on Poster designs.

I like sciposter. Some people prefer a0poster.