Buy a Macbook (or pro refurbished), run windows and mac on one of the lightest, fastest laptops on the market. (p.s apple seem to be updating the design of a lot of their products at the moment, so i might be tempted to wait).
I'm sorry. Macbooks are nice, even if the keyboard takes some getting used to and the screen is about average. But if you look at the 13.3" class, the Macbook is actually one of the heaviest. Take this from someone who owns a Sony SZ. That's 2.3kg for the Macbook vs. 1.8kg for the SZ. And there are lighter notebooks around than the SZ.
Generally, if you're tech-savvy, the Macbook is an option you should consider. Tech-savvy, that is, if you want to run Windows, because even with Bootcamp, it's going to take more effort and knowledge than a laptop with Windows pre-installed. Design-wise, they're gorgeous and if you like OSX, then go ahead.
Apart from that, I never liked the HP laptops, the ex-Compaq models are sort of nice but way out of your price-range. Lenovo is awesome, these things are built like a tank and the tech support is the best ever. I can also really recommend Samsung, at least in Europe, they've got great prices and a very good tech support.
Stay the fuck away from Sony unless you know that you can perform most repairs yourself (unless it's a real hardware failure).
Generally, I would only buy notebooks from big companies because tech support is something you have to rely on in a notebook, especially for all things hardware. You can't fix these things yourself (Software-wise and some hardware, you can, if you know what you're doing), so make sure the company has a good reputation. And generally, small companies only re-badge barebones sold by big OEMs from Taiwan. The support and development structure isn't as developed and you might be stuck with people who don't know what the hell they're doing or parts that run out after one year.
Also, before buying a notebook, try it in a store for some time. Play with the lighting, the screen settings, the keyboard and sturdiness of the entire thing. These are things that will annoy you later on, so make sure to check on them beforehand. I can't stress that enough, because I've seen tons of people complaining about these things because they only bothered to check for about one or two minutes.
