This site has several different activities that correlate to different textbooks. I found that the activities are still quite good even for a different textbook than the one in your class.
An upper level textbook supplemental website, but great for giving background information and cross-curriculum lessons for introducing the Renaissance era and literary pieces.
This is a good site for an upper level chemistry course...perhaps an AP chemistry or a college chemistry class. An honors chemistry class might be able to do this with guidance. I think this would be a good website for explorative learning by themselves or as supplement to the textbook
YourTeacher.com offers a comprehensive library of Algebra 1 lessons featuring a personal math teacher inside every lesson. Can connect to different textbooks and other subjects.
This is another website that contains lesson plans in Mathematics, along with other content areas. Many of them require the students to use a computer or some other form of technology. There are also some lessons with integrated subjects other that math.
This site is the home page for using new technologies to enhance learning. There is an online textbook and primary sources. There is also a section for teachers and an active learning section too.
This is a good website for history teachers. There are a lot of resources on here about how to teach specific topics. They have handouts, primary sources, how to motivate students for certain material etc. and there are a lot of different topics to choose from.
This site is really helpful for students reading Poe's "The Fall of the House of Usher," as it provides pop-ups with vocab, info, reading questions, etc. that help the student understand Poe's story