Are any of the brands of memory considerably better than any of the others? Should I worry about that, or should I worry more about the actual memory I'm getting.
Some manufacturer's enjoy a better reputation than others, but it's like automobile manufacturer's, they all build a good car, but some build high performance cars as well. If you were going to be overclocking I would go with something like Crucial's Ballistix, this would be their high performance modules.
Another consideration would be if you have a motherboard that is capable of running in dual channel. If you are going to run modules in dual channel you will want to have matching modules for the best performance.
i recently bought 2gb pny ddr2-800 pc2-6400 dual channel ram for only $39.99 at http://www.newegg.com
pny, kingston, corsair, crucial, hp, dell, g.skill, samsung, and other known brands are great. never buy cheap @$$ ram, it will give you cheap @$$ performance and cheap @$$ quality lol :)