Laser induced plasmas can be formed from the focused output of high power pulsed sources. Depending on the wavelength and pulse duration, different mechanisms are responsible for the plasma generation. I will summarize our recent studies on laser plasma formation with ultraviolet and near-infrared nanosecond pulses. Measurements of energy absorption, optical luminosity, and Rayleigh scattering thermometry show different threshold behaviors for different pulse conditions. These types of laser plasmas are of practical interest for ignition of combustible mixtures, for example for reciprocating gas engines, aeroturbines, and rocket engines, with potential benefits including increased combustion efficiency, reduced pollutant emissions, and increased reliability. I will also present results of combustion ignition using nanosecond laser pulses including new dual-pulse and multi-wavelength schemes.