Physical Constants

Plank's Constant	h = 6.6260755 x 10-34 J s
	h-bar (h/2*pi) = 1.05457266 x 10-34 J s
Boltzmann's Constant	kB = 1.380658 x 10-23 J/K
Electron Charge	e = 1.60217733 x 10-19 C
Avogadro's Number	NA = 6.0221367 x 1023 particles/mole
Speed of Light	c = 2.99792458 x 108 m/s
Permeability of Free Space	mu0 = 4*pi x 10-7
	mu0 = 12.566370614 x 10-7 T2 m3 / J
Permittivity of Free Space	epsilon0 = 1 / mu0*c2
	epsilon0 = 8.854187817 x 10-12 C2 / J m
Fine Structure Constant	1/alpha = 137.0359895
Electron Rest Mass	me = 9.1093897 x 10-31 kg
	me = 0.511 MeV/c2
Proton Rest Mass	mp = 1.6726231 x 10-27 kg
	mp = 938.26 MeV/c2
Neutron Rest Mass	mn = 1.6749286 x 10-27 kg
	mn = 939.55 MeV/c2
Atomic Mass Unit	u = 1.66057 x 10-27 kg
	u = 931.43 MeV/c2
Bohr Radius	a0 = 5.29177 x 10-11 m
Electron Radius	re = 2.81792 x 10-15 m
Gas Constant	R = 8.3143 m2 kg / s2 K mol
Molar Volume	Vmol = 22.41383 m3/kmol
Gravitational Constant	G = 6.6732 x 10-11 m3 / kg s2
Acceleration due to gravity	g = 9.81 m / s2
Compton Electron Wavelength	lambdac = h / me c
	lambdac = 2.42631 x 10-12 m

(Table adapted from a table by Burkhard Kirste)

More, and more standard, constants may be found here