I prefer a Pentium M processor in a laptop. It's faster and cooler than most other chips for the same performance. An Athlon 64 in a laptop woul have pretty bad battery life.
I have a Dell laptop and have been pretty happy with it, aside from wishing I'd gone for a slightly larger HDD.
Also, make sure to get at least 512MB of RAM, if you get 256MB, you'll be swapping stuff to disk, and that uses up your battery.
Shared video RAM just means that the video board doesn't have its own RAM, so it uses your system RAM. This is usually found in lower-end graphics cards, so if it uses 64MB of shared video RAM, it might eat
up to 64MB of your system RAM. Laptops aren't the best for high-resource-usage games anyway, so this may not really be an issue unless you really want to play UT2004 on it. It basically depends on how you use it.
You can't just dismiss an entire company by one component that they offer. If the Pantster was more familiar with Toshiba, he'd be aware that you can customize your laptop. Check out
Toshiba's direct-sales site (toshibadirect.com) to see what I mean. Some options use shared video memory, some use dedicated.
Also, there's nothing wrong with Dell, either. They have a reputation for size because of the Inspiron series, which pioneered the "large notebook"/desktop replacement category, but these days pretty much every company has a desktop replacement line. And I suspect the "weird stuff" that the Pantster is referring to is from Ebay or something, because Dell's options are about the same as everyone else's.
I'd suggest visiting your local Best Buy or the like to see what kind of size you prefer - for my own part I like 14.2", but others may prefer larger or smaller screens. Also, you'll get acquainted with the size of the unit as a whole. My Dell is about average size for a mainstream laptop, but my mother's laptop is a significantly larger Toshiba desktop replacement laptop. (not meant to move around as much) My father has an ultralight laptop from his work. (an IBM Thinkpad) Look for a series name and model that looks like what you want, then go to the company's site and see if you can customize that particular model of that particular series to what you want.
Also, if you have a choice in the batteries, get the largest battery you can. An optical bay battery has come in handy for me, because I can slip it in and avoid losing work when my main battery is low.
I'd suggest using Windows XP Pro, it's easier to fix certain things without going into the registry. If you pm me after you get the laptop, I'll show you how to tighten it down so it's less resource-wasteful and insecure.
(also, you'll want to get a decent lock for your laptop if you plan on going places without it. For that guy. You know. Justin Case.)