Carry on luggage, international travel - travel bag measuring 26" x 15" x 9 is allowed as carry on?
also, I know we're allowed 2 carry on bags, is this correct?
Air travel, of course 
Check with your carrier, but for most airlines it is something like about 45 linear inches (height + width + length has to add up to less than 45 inches total). Others will tell you no bigger than 24×16x 10 inches. I will say, that I recently traveled southwest, and they wouldn't let me keep my book bag on the plane. I think they were just being dicks but I'd call them ahead of time.
Gravis Jetway Rolling Luggage, Travel Bag - Overview