Arxiv - All your physics/math/astronomy preprint needs.
Google Directory: Science - Google has a great guide to all kind of science links. If you can't find it here, you probably can't find it anywhere.
Scirus - A scientific search engine. It's good for searching only in journals or educational sites.
Internet FAQ Archives - A database of Usenet FAQs. This includes a lot of scientific FAQs.
HowStuffWorks - This site has good explanations of all sorts of things.
MIT OpenCourseWare - "A free and open educational resource for faculty, students, and self-learners around the world." Yes, 700+ free university-level courses for you to download.
Nature Journal - Probably the most well known scientific journal. There are some free articles on their site.
SparkNotes - Study guids for a lot of different subjects.
The Journal of Modern Problem Solving - "The journal provides a source of modern problem solving for students and teachers from grade school through grad school and beyond in all subjects that use mathematics for problem solving." This site offers a lot of great examples how to solve scientific problems. It has different sections for math, physics and chemistry. These sections are also mentioned in the other categories.
[edit on 19-8-2004 by amantine]
[edit on 19-8-2004 by amantine]


