Expect to spend at least $750 on a laptop capable of casual gaming ...
You'll want at least:
ATI Radeon HD 2600/HD 3650 or better
Nvidia GeForce 8600/9500 or better
ATI's cards run cooler and draw less power, so they're a better choice on a laptop, even if the equivalent Nvidia cards are a little faster.
Personally, I'd recommend an Intel 7000/8000/9000 series Core 2 Duo. On a more budget friendly scale, the Core 2 Duo T5750/5850 are decent as are the Turion Ultra X2 RM/ZM CPUs.
3 GB or more is plenty of RAM
I'd aim for a newer 7200 RPM hard drive, though it's not a common feature.
Best bang for the buck I've seen is the Gateway T6873/4 ... T5750, 3 GB, HD 2600, 320 GB, Vista Home Premium for $800 ... Personally, I'd rather get an HP or Dell equivalent, which will probably run you about $1000 ...
Oh, and Toshiba is god awful ... We send back at least a dozen laptops a month from DOAs and the ones that survive the first month don't exactly have a stellar track record, either ...