There has been some coverage in the news of the potential threat of deflation, an area of which we know less:
Here are links to Fed speeches and papers on deflation (from Dave Backus):
On deflation, here is a recent speech:
http://www.federalreserve.gov/BOARDDOCS/SPEECHES/2002/20021121/default.htm
Here are some academic sources:
http://www.minneapolisfed.org/publications_papers/pub_display.cfm?id=3350
http://www.minneapolisfed.org/publications_papers/pub_display.cfm?id=931