Are there any tablets, like the very nice looking but non-USB provided iPad, that actually have a USB port to allow external things to be connected?
Some examples
Asus EEE Slate EP121
Fujitsu Q550
Lenovo Thinkpad Tablet
Lenovo Ideapad K1
Lenovo Ideapad P1
Lenovo A1
Tablet Kiosk (Oooh, an i7 CPU)
Samsung
Toshiba
Etc etc etc
Otherwise you have to look at Dell/Fujitsu/Lenovo/etc machines which are, basically, laptops with a touchscreen.
Look here (page 1 of 3)
The biggest issue with having a USB port on a tablet is then you make the tablet thicker, and that goes against the concept of "thin is beautiful" which is all the rage nowadays, and that's why they don't fit them to things like the iPad (as well as the manufacturers who do not fit USB ports being able to charge an arm, leg and testicle for the "hub" which you add which allows you to have USB ports).