generally USB 3 ports are coloured blue
click on the image to see what I mean
http://www.jaycar.com.au/productView.asp?ID=XC4947
they are also usally only found on the latest laptops and even then usally only one or two with the rest being USB 2 (they are backwards compatiable with all USB but you can't connect a USB 3 device into a USB 2 port as it won't work.
USB 3 is the way of the future coming to a computer near you soon they offer data transfer speeds of up to 4.8Gb/s with plans to upgrade this to 10Gb/s by mid to late 2013. All the connections (apart from the normal USB port connctions) are different from USB 2 i believe also