IBM all the way, and laptops are my bread and butter, I've worked with tons of different ones over the years. If you don't mind something that's a little outdated then go look on overstock.com, they have alot of IBMs over there for cheap.
T series, the T4x is the latest line. You can buy all over the place, I get mine from CDW usually. Overstock.com has a bunch of older ones for cheap right now. An IBM is going to cost more than many of the other brands, but the quality is top notch. Dell has some good deals now too but I've never been impressed with their cases.
I tend to like Dell because price/performance/customization has always been top of the line. In fact, you can usually get the "latest tech" in a Dell Inspiron 6 months to a year or more ahead of IBM. IIRC, I had a high res 15" screen for nearly 2 years before anything even close was offered on an IBM. Same for faster hard drives, memory/chip upgrades, and all the rest. However, IBM has a MUCH stronger case and a better keyboard in general. Another beef I have with IBM is their required proprietary config software that is buggy as crap and the fact that they have steadfastly refused to provide the "windows" key compatibility even from within their "custom" (but VERY limited) key mapping. Toshiba has a good mid range line, but not as much customization as Dell, though seems Dell customization is way down lately, you can't hardly get anything without being stuck with a "wide screen". If all you want is "pretty" and multi-media with great portability, the Vaio I'm told is good. The others aren't even on my radar...
I second IMB. The thinkpads are pretty damn nice and have the best mouse pointer device I have ever used in a notebook.
Ive been very happy with my Dell's over the years. The laptop im typing this from nearly 2 years old, and hasnt missed a beat yet. I'll be upgrading shortly to another dell, but something smaller and lighter, this one is sortof bulky. I have dropped this one more than once, had gear puller fall on it from a few feet up, introduced the keyboard to a beverage of an alcoholic nature, and suprisingly it still works fine, although it does have a dent in the case. Yes, im hard on my computer, but it doesnt see 1/4 the abuse of my camera's. :doah: Ive heard good things about Toshiba and the Sony's, and mixed reviews on the IBM's. I know several people who love them, and others who dont. Everybody i know dislikes Compaq's, and ive been told to stay away from them by many people. Bottom line, im happy with my dell's, but havent owned anything else, other than a Tandy 2000 from 1979, so i really dont have much to compare it to.