This detailed article in Geospatial World by Anusuya Datta provides an extensive listing and description of a variety of free lidar data sources from around the world, as well as this informative introductory video.
The USGS 3DEP program is the leader in this effort to democratize lidar data here in the U.S. Along the coast NOAA’s Digital Coast covers over 550,000 sq. miles with contributions from the U.S. Army Corps of Engineers and the National Geodetic Survey.
A group that I have not heard of is the United States Interagency Elevation Inventory which is collaboration of the USGS and NOAA. They provide an inventory of high-accuracy topographic and bathymetric data for the U.S.
There are a number of other resources including sources in the UK, Netherlands, Finland and Spain.