Science and technology from Oxford Reference Online [24/7] [Can't get in?]
How Stuff Works - Clear descriptions of the workings of all kinds of technical, scientific, and social phenomena [Title index of all articles].
BBC Science & Nature - Information supporting and complementing the content of the BBC's current and previous scientific programming.
New Scientist - Current scientific news and information from the prestigious and popular science journal. Also lists articles from earlier years on topics of current concern.

Access to Research - Free online access within public library buildings to thousands of academic journals.
Scientific Calculator - A nice simple fully functional scientific calculator you can operate via the web from calculator.net

Arkive - "A Noah's Ark for the Internet era": information, images and multimedia concerning the world's endangered wildlife.
Birds: Avibase provides lists of birds found in countries from around the world giving pictures, names, descriptions and numbers of species. Birdforum is an online community for those interested in birds where people can share what they have seen with pictures and messages.
Online Atlas of the British and Irish flora - brings together information on the distribution and ecology of the wild flowering plants and ferns of Britain and Ireland
Plants for a Future - Major database of plants having medicinal, culinary, horticultural, or other uses. Includes detailed information on propagation and cultivation, and links to other sources of information on the web.

Internet Chemistry and Internet Physicist - 'Teach-yourself' tutorials on Internet information skills for those studying chemistry or physics. Part of a wide range of subject-specific tutorials from the Virtual Training Suite.
Periodic Videos - An explanatory video about each of the elements in the Periodic Table - featuring experiments, examples and big hair!
Chemical Elements.com - Interactive periodic table, which can be configured to display the different characteristics of elements, or different elements by group.
physicsworld.com - the magazine of the Institute of Physics, with archive of articles on all aspects of physics.

Internet mathematician - A 'teach-yourself' tutorial on Internet information skills for those studying maths. Part of a wide range of subject-specific tutorials from the Virtual Training Suite.

NASA - Comprehensive web of information from the official North American Space Agency.
The Night Sky – things to look out for in the night sky, updated monthly by Jodrell Bank

MatWeb - Database about materials used in manufacturing, including information about properties, trade names and manufacturers.
How Products Are Made - Detailed descriptions of how manufactured products work, and how they are made, with an alphabetical index and a search box.