A landslide is defined as "the movement of a mass of rock, debris, or earth down a slope" (Cruden, 1991). Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity.
The best place for this sort of information is the National Centers for Environmental Information, which is part of the National Oceanic and Atmospheric Administration of the U.S. Department of Commerce.
Landslides are a serious geologic hazard common to almost every State in the United States. It is estimated that in the United States they cause in excess of $1 billion in damages and from about 25 to 50 deaths each year.
Yes, in some cases human activities can be a contributing factor in causing landslides. Many human-caused landslides can be avoided or mitigated.
Every state in the US has a geoscience agency and most have some landslide information. The Association of American State Geologists provides links to the State Geologist for every state.  
The Thistle, Utah, landslide cost in excess of $200 million dollars to fix (1984 dollars – adjusted for inflation this would be more than $400 million in 2010 dollars).
In the United States, it was estimated in 1985 that the total dollar losses from landslides average between $1 billion and $2 billion per year.
An average of between 25 and 50 people are killed by landslides each year in the United States. The worldwide death toll per year due to landslides is in the thousands.
An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions.
Data for rainfall, ET, and water-level height at gages can be explored, searched, and downloaded using a new online tool called Explore and View EDEN (EVE).