How CS Master's Funding Works (and Why You Can't Seem to Get Any)
First version: 2008-08-05.
You're coming to the US for a master's degree in computer science. You wonder why some schools offer financial aid while others, such as Brown, don't, and whether you can get any. I can't actually answer your question, but I can tell you a little about how the process works so you can understand your situation better, and what if anything you can do about it.
In terms of financial aid, the master's degree is viewed strictly as a professional degree. The aim of the program is to enable students to improve their skills and credentials and to therefore seek better-paying jobs. As with all professional degrees, there is therefore little incentive to pay students doing degrees purely for their self-enrichment. In the US, the expectation is that students will take out appropriate external financial support with the intent of using their subsequent (higher) earnings to pay it back—a sort of direct investment in oneself.
The issue is complicated further by the means we have for funding. Our financial aid comes in the form of grants from the US National Science Foundation and similar bodies. This money is given for specific research projects. In my experience (and generally, that of most faculty), a master's student cannot productively contribute to such projects in the short time they are here. It takes a year or two just to get up to speed—and just when they are ready to be productive, they graduate. (In contrast to PhD students, who are then around for three to four years of very high productivity.) Therefore, spending research grants on master's students would be a misuse of these funds.
The other complicating factor is that master's students spend most of their time taking classes, since their goal is to graduate soon. Therefore, even if a student were qualified to perform research, they would have very limited time to do so. In contrast, again, a PhD student faces the same problem for the first year or two, but then takes virtually no classes subsequently, thereby amortizing the cost of those classes.
That said, this also identifies an opportunity. For some projects, some students have just the right background—especially for projects that can exploit whatever industrial experience they have. In such cases, a student can indeed be productive very early on, and therefore may be able to make a case to an advisor. It would be up to the individual student and advisor to find such opportunities—there is no general mechanism for that.
If you find yourself in this position, I would advise that before you try to ask a professor about money, first demonstrate your value. Speaking both for myself and generally, a professor's general instinct when asked about funding is to be evasive or negative, since they don't want to give a student false hopes. But if you perform superbly, going well beyond the call of duty (academically, that is: e.g., by doing all the course assignments well, taking on any extra-credit homeworks that are given, asking for and then actually reading research papers, etc.), and then ask a professor whether they have funding, there's a small chance that by then the prof is already looking at you with a glint in their eye. This is the situation you should be aiming for.