Below is a table of different wavelengths and what gas combination generate them.  See the list after the jump.

                                                    Wavelength (nm)
        Laser Type                                  Approx.     Exact    Notes
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   Fluorine (F2, Excimer-UV)                         157       157.48
   Argon Fluoride (ArF, Excimer-UV)                  193       193.3
   Krypton Chloride (KrCl, Excimer-UV)               222       222
   Helium-Silver Ion (HeAg+)                         224       224.3
   Krypton Fluoride (KrF, Excimer-UV)                248       248.4
   Neon-Copper Ion (NeCu+)                           249       248.6
   Frequency Quadrupled Nd:YLF (UV)                  262
   Frequency Quadrupled Nd:YAG (UV)                  266
   Xenon Chloride (XeCl, Excimer-UV)                 308       308.17
   Helium-Cadmium (HeCd, UV)                         325       325.029
   Nitrogen (N2, UV)                                 337       337.1  Multiple
   Xenon Fluoride (XeF, Excimer-UV)                  351       351
   Frequency Tripled Nd:YAG (NUV)                    349
   Frequency Tripled Nd:YLF (NUV)                    351
   Frequency Tripled Nd:YLF (NUV)                    355
   Calcium Vapor Ion (NUV)                           374       373.690
   Gallium Nitride (GaN, NUV to violet)            400-410       -
   Gallium Nitride (GaN, violet-blue to blue)      430-445       -
   Strontium Vapor Ion (violet)                      431       430.544
   Helium-Cadmium (HeCd, violet-blue)                442       441.565
   Frequency Doubled Nd:YVO4 (blue)                  457
   Frequency Doubled Nd:YAG (blue)                   473
   Krypton Ion (Kr+, blue)                           476       476.243
   Argon Ion (Ar+, green-blue)                       488       487.986
   Xenon Ion (Xe+, green-blue)                       499
   Copper Vapor (Cu, green)                          510       510.554
   Argon Ion (Ar+, green)                            514       514.532
   Krypton Ion (Kr+, green)                          520.8
   Xenon Ion (Xe+, green)                            526       526.012
   Krypton Ion (Kr+, green)                          530.8
   Frequency Doubled Nd:YLF (green)                  523
   Frequency Doubled Nd:YLF (green)                  527
   Frequency Doubled Nd:YVO4 (green)                 532
   Frequency Doubled Nd:YAG (green)                  532
   Xenon Ion (Xe+, green)                            542       541.915
   Helium-Neon (HeNe, green)                         543       543.5161
   Frequency Doubled Nd:YAG (yellow-green)           561
   Helium-Mercury (HeHg, green)                      567       567.717
   Krypton Ion (Kr+, yellow-green)                   568       568.188
   Copper Vapor (Cu, yellow)                         578       578.213
   Sum Frequency Nd:YVO4 (1342+1064, yellow)         593
   Helium-Neon (HeNe, yellow)                        594       594.09633
   Helium-Neon (HeNe, orange)                        612       611.97087
   Helium-Mercury (HeHg, red-orange)                 615       614.947
   Gold Vapor (Au, orange-red)                       627       627.8170
   Helium-Neon (HeNe, orange-red)                    633       632.81646
   Krypton Ion (Kr+, red)                            647       647.088
   Alexandrite (red-NIR)                           655-860               (8)
   Gallium Aluminum Arsenide (GaAlAs, red to NIR)  670-830
   Chromium:Sapphire (Ruby, Cr:AlO3, red)            694       694.3
   Chromium:LiCaF (Cr:CaF, NIR)                    720-840
   Chromium:LiSAF (Cr:LiSrAlF6, NIR)               780-920
   Chromium:LiSGaF (Cr:LiSGaF, NIR)                  820
   Gallium Arsenide (Gaas, NIR)                      840
   Titanium:Sapphire (Ti:Sapphire, red to NIR)     675-1,100     -
   Neodymium:YVO4 (Nd:YV04, NIR)                     914
   Neodymium:YAG (Nd:YAG, NIR)                       946       946
   Ytterbium:KGW (Yb:KGW, NIR)                   1,026-1,024     -
   Ytterbium:YAG (Yb:YAG, NIR)                      1,031    1,029.6
   Neodymium:YLF (Nd:YLF, NIR)                      1,047
   Neodymium:YLF (Nd:YLF, NIR)                      1,053    1,053
   Neodymium,Chromium:GSGG (Nd,Cr:GSGG, NIR)        1,061    1,061
   Neodymium:Glass (Nd:Glass, silica glass, NIR)    1,062
   Neodymium:LSB (Nd:LSB, NIR)                      1,062    1,062
   Neodymium,Chromium:LSB (Nd,Cr:LSB, NIR)          1,062
   Neodymium:YAG (Nd:YAG, NIR)                      1,064    1,064
   Neodymium:YVO4 (Nd:YV04, NIR)                    1,064    1,064
   Neodymium:KGW (Nd:KGW, NIR)                      1,067    1,067.2
   Neodymium:YAG (Nd:YAG, NIR)                      1,122
   Helium-Neon (HeNe, NIR)                          1,152    1,152.5900
   Neodymium:YAG (Nd:YAG, NIR)                      1,319    1,318.7
   Neodymium:YVO4 (Nd:YVO4, NIR)                    1,342    1,342.5
   Erbium:Glass (NIR)                               1,540    1,540
   Thulium:YAG (Tm:YAG, MIR)                     1870-2160       -
   Thulium,Chromium:YAG (Tm,Cr:YAG, MIR)            2,013    2,013.2
   Thulium:LuAG (Tm:LuAG, MIR)                   2,020-2,030             (9)
   Holmium,Thulium:YLF (Ho,Th:YLF, MIR)          2,047-2,059            (10)
   Holmium:YLF (Ho:YLF, MIR)                        2,060    2,050.5
   Holmium,Chromium,Thulium:YAG (Ho,Cr,Th:YAG, MIR) 2,090    2,091
   Holmium:YAG (Ho:YAG, MIR)                        2,100    2,098
   Hydrogen Fluoride (HF, MIR)                      2,700    2,700
   Erbium:YAG (Er:YAG, MIR)                         2,940    2,940.3
   Helium-Neon (HeNe, MIR)                          3,391    3,391.2224
   Deuterium Fluoride (DF, MIR)                  3,600-4,200            (11)
   Carbon Dioxide (CO2, FIR) (12)                   9,600    9,600    Multiple
   Carbon Dioxide (CO2, FIR) (12)                  10,600   10,600    Multiple

(source http://www.repairfaq.org/sam/laserioi.htm#ioicav)