Good luck for under $1000. If you're careful and not rough, you can probably get by with a cheaper notebook that isn't built quite so sturdy, that might save you a few dollars.
Suggestions:
Get at least 1 GB, RAM is cheap these days, even from crucial.com
Get a real GPU, at least a 128 MB X1600, don't skimp on the graphics, you'll be kicking yourself later. "Upgradable" graphics can be upgraded, at a huge price.
If you plan on outputting your animations to MiniDV, DVCAM, or DVCPro, then get a notebook with a Firewire/iLink/IEEE1394 port.
Built-in bluetooth is handy, that way you can bring along a good mouse without also having to bring along a wireless adapter or cord.