General:
As a general rule, all illuminants are compared against the spectral energy distribution of the so called blackbody radiator, an artificial temperature radiator that radiates light with a specific color at defined temperatures, unit [K]. While this is supposed to be a reference for incandescent lamps, it is often used as a reference for other light sources as well. 
Please keep in mind that for all others (e.g. the D-illuminants) these values are relative and defined with a “correlated color temperature” (CCT).
Additional information about CIE illuminants can be found in CIE 15:2004.

Daylight illuminants:
Illuminants that represent daylight conditions; the ones most widely in use today are:

C: old standard for average daylight from the northern sky, defined in 1931 by the CIE with a CCT of 6774K; has a significant lower UV content than the D-types; does not have CIE status of “standard illuminant” anymore

D50: first defined in 1974, and in 1975 certified by the ISO:3664, this daylight illuminant is the reference for the printing and graphic arts industry, CCT 5003K (ISO revised in 2009); does not have CIE status of “standard illuminant”

D65: defined in 1964, D65 has become today’s standard daylight (average noon daylight from the northern sky) reference for the industry for various applications with a CCT of 6504K; described and referenced in ISO:3668, ASTM 1729 and DIN6173-2

By definition, the CIE and ISO state that the “CIE standard illuminant D65 should be used in all colorimetric calculations requiring representative daylight, unless there are specific reasons for using a different illuminant.” (ISO 11664-2:2007(E)/CIE S 014-2/E:2006)

Incandescent / tungsten lamps A: defined in 1931 as a CIE “standard illuminant”, illuminant A is intended to represent typical, domestic, tungsten-filament lighting. Its relative spectral power distribution is that of a Planckian radiator at a temperature of approximately 2856K.

Fluorescent lamps
12 fluorescent lamp types were defined by the CIE, named F1-F12, being different in the combinations of gases used and phosphors they are covered with. Among these 12, 3 are most commonly used in the industry and as such, are most important for colorimetric evaluations.

F2: also named “CWF” (cool white fluorescent), these lamp types have a CCT of 4230K and make up a majority of typical office illumination

F7: broad-band fluorescent lamp, approximation of D65 with a CCT of 6500K

F11: also known under the name TL84, this fluorescent narrow tri-band type resembles or is mostly used as warehouse lighting and has a CCT of 4000K