It doesn’t really matter too much these days. I would recommend any laptop/desktop that has:
4GB+ of RAM (DDR2 or DDR3)
dedicated graphics memory(eg. nVidia Geforce GxxxM, nVidia Ion)(the more the better)
A 2GHz+ Dual/Quad Core Processor (eg. Intel Duo 2, Intel Atom) (faster is better)
At least 250GB Hard Drive (so you have plenty of space for art assets)
Bear in mind, that it depends on what software packages you need to use. Particularly If your creating your own assets. Simply put, faster and more of it is better.
As for SSD: This would only improve loading times eg. when you have a lot of assets.
Personal Experience:##
Two years ago I bought a ASUS K50IN Laptop for about £400 ($622 US). It had the that same specification that I mentioned. Runs like a dream with Unity and Blender, Maya etc… It wasn’t massive in size, it only had a 15.6" screen (1366x768) and is about 3kg (6.6 Pounds). I was on offer when I bought it.
It’s not much of an answer, but I hope you it helps you.