Unclear what age you're aiming at, but I like all the sites mentioned for older kids (7 and up). If you're talking about younger kids (3-6), who will outgrow the skis in a year or two, think about used rentals on ebay. You can score 70-110 cm skis with good bindings in nice condition for $40-60 during the late spring early summer. (Resorts need to have some around, but few kids that age actually ski, so the rentals are underused.)
Incidentally, far as I know, Fischer and Elan make most kids' skis < 100 cm under contract to the other companies. So the only real differences will be in graphics and very minor design diffs in the bindings. Boots, OTOH, need to be new, according to my pediatrician. Again, looks like most are made by one or two companies - suspect Solomon - and only real variation beyond colors is that larger (older) sizes have more than one buckle, and you begin to see split between rec and race when you reach sizes intended for 7 and up. Good luck!