It's difficult to give any recommendations for a certain laptop model in general. Your personal needs have to be taken into account. Also the market is changing very quickly. I guess every three months a new generation of laptops (with bigger harddisk space, higher CPU speed, more display size, etc.) comes into the market. So I don't give any model or brand specific recommendations. But you may check my Linux support of laptop and notebook manufacturers survey.
A good way to check Linux hardware compatibility the next time you go shopping a laptop is using a Knoppix CD/DVD. The Knoppix hardware detection works quite well and is often capable to check all laptop hardware.