I got HP's dv9000t about a month ago, and it's been great so far considering its price. Custom building it on Costco's site, for $1330 I was able to get it with the following specs:
2.0 GHz Centrino Core 2 Duo (4 MB cache), 512 MB RAM, Nvidia Geforce 7600 (256 MB), 120 GB HD (5400 RPM)
After that, I spent $70 for another GB of RAM, totaling to 1.5 GB RAM (which is just perfect for pretty much anything). I also bought a copy of Windows XP OEM for $100, meaning that my total cost was $1500. I could have saved several hundred dollars had I gotten a slower processor, but this one had a larger cache and that was worth the extra money for me. Considering that this is a 17-inch notebook, this was pretty cheap, as most 17-inchers usually cost upwards of $2000. The dv9000z offers faster processor speed at an added price, but I prefer the t's Intel processor to the z's AMD.
17-inches is fairly large, which means that while it makes a great entertainment machine, it might be a pain to use on the go. (I usually don't have much trouble carrying it around, but it's not something that I can easily whip out and crunch a few numbers on in a pinch.) It also has more limited battery life, ~2 hours. If you want something smaller, HP's 6500t is 15.4 inches and will probably be quite a bit cheaper.
One thing about specs: Notebook manufacturers almost always overcharge for components, which means that the more components that you can do after-market upgrades on, the better. This is especially true of RAM, since it's stackable. I highly advise against buying something with 2 GB of RAM; there's not much difference between 1.5 and 2 GB. More importantly, if you can find a machine with 512 MB and then add another GB (which should cost around $70), you can save yourself around a hundred dollars. (This is what I did.) Also, about what Nate said about hard drives: the added performance added by having a 7200 RPM hard drive (rather than a 5400 RPM) one is really only significant when booting or if you have a heavily fragmented hard drive, and will cause your battery life to take a huge nosedive. If you care about battery life, stick with a 5400 RPM hard drive, although 7200 RPM works great if you're only worried about performance. As for capacity, get as little as you can afford to. Laptop hard drives offer very little space for your dollar (especially if you're getting a 7200 RPM one) and if you've got a lot of movies and such, it might be worth your while to get an external hard drive (if you don't have one already). An iPod works in a pinch.
Macs are nice, but really quite expensive. In short, don't buy a Mac unless you want to use OS X (which really isn't a bad idea at all).
