well, streetlight isn't really ska. they consider themselves to be inspired by many different genres, one of the more prominent being ska.
but there are really no bands that are similar to streetlight. as someone said before, your best bet is with...
some favorite ska / punk / reggae bands:
streetlight manifesto, andrew jackson jihad, the aquabats, b.o.t.a.r, bad brains, big d & the kids table, black flag, blue collar special, bob marley, the bouncing souls, catch 22, the clash, common rider, desmond dekker, then expendables, fatter than albert, fishbone, five iron frenzy, flaming tsunamis, gimp, goldfinger, the hippos, iration, less than jake, mad caddies, madness, the mighty mighty bosstones, mustard plug, the misfits, nofx, operation ivy, pepper, the pietasters, the planet smashers, the ramones, rebelution, reel big fish, screeching weasel, the scruvy knaves, the skatalites, the specials, the suicide machines, the toasters, voodoo glow skulls
(that's not all)
some other musical favorites:
arctic monkeys, atom and his package, audio adrenaline, avenged sevenfold, the beatles, bob dylan, bobby mcferrin, bon jovi, cake, camerata academica, christopher "isto" white, chronic future, chumbawamba, creedence clearwater revival, dead milkmen, earth wind & fire, gogol bordello, hot hot heat, the hues corporation, jack johnson, jackson 5, jet, johnny cash, kc and the sunshine band, the killers, korn, mercyme, michael jackson, mika, mozart, muse, nine inch nails, nirvana, of montreal, queen, rage againt the machine, red hot chili peppers, relient k, seven wiser, simply red, smashing pumpkins, stevie wonder, stereogram, the strokes, they might be giants, the untouchables, the used, the von bondies, war, ween, weezer, the white stripes
(that's not all)
I am a...
SKA Enthusiast, Unique Individual who can not be categorized