I was pleasantly surprised to see that Ubuntu listed several laptops on their site that would work with their distro so I ended up getting a Dell Inspiron 15 which I re-partitioned. After that I installed Ubuntu 11.04 without a problem and everything works after installation.
Wife and kids use the Windows 7 partition and I use the Ubuntu partition when I use it which is actually quite often. The machine is obviously not as nice as a Macbook Pro but it costs only a third of what the smallest Macbook Pro costs and as far as I've been able to tell it works just as well for most purposes.
If you're after a good Unix/Linux experience for a reasonable price I think this is a good option.