Environmental Science 2008 (blue book with butterfly): (the sample word is SCIENCE08, you then have to complete the rest of the areas to get 120 day access to the online textbook
http://preview.hrw.com/sample/reg_sample.jspPreCalc w/ Limits (5th edition): (the sample word is THINKWELL, again you have to complete the rest of the areas to get 120 day access)
http://preview.hrw.com/sample/reg_sample.jspWorld History: Ancient through Early Modern times: (the activation code is 2293467-40) (create a teacher account) (teacher code is MCD3P9T4LV47R, again you have to complete the rest of the areas to get access)... you just need to locate the book by the title above, click on the link and down at the bottom of the page it will say online book
http://www.classzone.com/cz/validate.htm