Curriki contains more than 19,000 resources submitted by users under 11 categories. Although it has a US bias, it is designed specifically for educational use. See www.curriki.org for the homepage and ww.curriki.org/xwiki/bin/view/Main/Browse for the subject search, which can filter by type of resource, level and file type. Some resources have been reviewed for quality, having been selected as excellent by users. Resource titles are often not helpful, but rest your mouse on them and a full description should appear.
Oracle, a database software company, have backed an educational library of 7000 suitable websites for education, arranged by subject and topic, with a review of each. See www.thinkquest.org/library for details.