According to USA Today, many major US retailers from Best Buy and Target to B&H Photo and Adorama are out of stock of the most popular DSLRs. Furthermore, it doesn't look like they'll be getting a large supply anytime soon.
Why? Many of the major camera companies - Canon, Nikon, Sony, Olympus, Panasonic and Pentax - produce SLRs and lenses in Japan and the production of DSLRs has stalled because of the Japan quake. Specifically, according to USA Today, the resulting rolling blackouts "has crippled production at many camera manufacturing facilities there". In fact, Canon says that they don't expect production facilities to return to normal until June or July. If you're looking for a camera, get 'em while you can. [USA Today]