With that budget you're limited. The iPad is definitely out of question which is a shame since it's the leading tablet for a reason. The RIM (BlackBerry) PlayBook is within your budget, it's an OK tablet but feels kind of unfinished. RIM have been promising updates for a while, they will happen, it's just taking a very long time.
The Samsung Galaxy is also out of your budget, but there are still tablets by ASUS and Lenovo that might be within your budget. Both of them run the Android operating system (Google) and are pretty comparable. Another option is the Amazon
Fire which is more of an eReader than a tablet, even though it's technically supposed to be a tablet - if that makes sense.
What do you want to do primarily with the tablet? Read? Surf the net? Play games? Watch movies?