I have at least one person a week ask me for assistance in picking out a laptop, and after all the time of looking around at what is available for the price, I just have a very hard time anymore suggesting anything but a business-line notebook or something higher-end from ASUS.
The most common notebook that we order is the HP EliteBook or the HP ProBook. They are unbeatable quality, and especially unbeatable value as any comparable Dell or even ASUS notebook is going to be several hundred dollars more. I just ordered an HP ProBook 4530s for a customer for less than $500 and has the build quality you will not find in any consumer laptop under $1,000.
One thing that was mentioned incorrectly earlier is the Core i3-2310M is not a quad-core processor, it is only a dual-core processor, but it does come equipped with HyperThreading. This means that the computer sees twice the number of CPU cores as what there actually is, so it will be more powerful than a straight-up dual-core processor when handling heavy multitasking or heavily-threaded applications, but it's still not going to be near as powerful as a true quad-core processor. That being said, the Sandy Bridge processors are much more capable (and energy efficient) than the previous generation of Core processors at the same performance/price point. If at all possible, I'd recommend the newer Sandy Bridge based systems, as all the other ones are basically end-of-life and will be disappearing very quickly.
I'm quite impressed at what a business-class $500 laptop can give you today. This one we just received in works well in photoshop, handles quite a few open applications and explorer tabs, and even offers several hours of battery life while just browsing around the web or typing up papers. Plus, you're dealing with the business side of the manufacturer, which is always going to give you better service and warranty replacement/repair options than the terrible consumer side of a manufacturer.
For the money, I will always recommend a business-class laptop, even with a budget as low as $500, and I've especially been impressed with the HP ProBook and EliteBook business class laptops.
http://www.newegg.com/Product/Product.aspx?Item=N82E16834157822