Please don't be put off by the amount of links, I don't know what standard you're at, that's why so many. Cherry pick the ones that are useful and disgard the rest. If you need specific help then you can e-mail me.
I have put together a large number of links that cover all the subjects that you are likely to be studying; I hope you find the sites useful.
http://www.how-to-study.com/
http://academickids.com/
http://www.gomath.com/
http://education.yahoo.com/college/essentials/practice_tests/sat/;_ylt=Arc8Qiu1CuMQYv2Ka30pK87ak7MF
http://www.newton.dep.anl.gov/archive.htm
http://highschoolace.com/ace/ace.cfm
http://www.multcolib.org/homework/
http://www.americaslibrary.gov/cgi-bin/page.cgi
http://www.2020site.org/
General Resources. ( HISTORY )
http://www.ipl.org.ar/cgi-bin/teen/teen.db.out.pl?id=gh1500
http://www.kipar.org/historical-resources/history.html
http://www.historyplace.com/homework/index.html
http://www.weatherheadhistory.ik.org/
http://www.history.com/
SCIENCES.
http://www.sciencenewsforkids.org/
http://sps.k12.ar.us/massengale/biology%20class%20notes2.htm
http://www.gregreeve.freeola.com/chemistry.shtml
http://www.liv.ac.uk/Chemistry/Links/reforganic.html
http://www.chemhelper.com/
http://www.highlightskids.com/
REFERENCE LINKS
http://www.homeworkspot.com/
http://education.yahoo.com/
http://school.discovery.com/homeworkhelp/bjpinchbeck/bjscience.html#anatomy
http://uk.ask.com/
http://highschoolace.com/ace/ace.cfm
http://www.multcolib.org/homework/
http://www.universalteacher.org.uk/default.htm
http://www.primaryresources.co.uk/index.htm
http://edtech.kennesaw.edu/web/3-5.htm
http://homework-help.aol.com/
http://www.studygs.net/
http://www.studygs.net/tstprp1.htm
http://www.actstudent.org/testprep/tips/index.html
http://www.hehs.d211.org/academics/english/testprep.html
http://www.virtualsalt.com/
http://www.world-english.org/
http://www.nationalgeographic.com/index.html
http://www.homeworkspot.com/
http://www.collegeboard.com
http://www.princetonreview.com
http://www.edhelper.com/
Great Internet Resources for Students
http://www.isd77.k12.mn.us/resources/sturesources.html
BOOK REVIEWS & SUMMARIES.
http://www.pinkmonkey.com/studyguides/subjects/sat/contents.asp
http://www.sparknotes.com/
http://www.gradesaver.com/
http://summarycentral.tripod.com/
http://www.antistudy.com/
http://www.cummingsstudyguides.net/
http://www.freebooknotes.com/
http://www.bookwolf.com/
http://www.cliffsnotes.com/
The Internet Public Library
http://www.ipl.org.ar/cgi-bin/teen/teen.db.out.pl?id=gh0000
Learn about the Common SAT pitfalls and how to avoid them.
http://education.yahoo.com/college/essentials/practice_tests/sat/;_ylt=Arc8Qiu1CuMQYv2Ka30pK87ak7MF
http://www.my-sat.com/
http://www.my-sat.com/index.html
http://www.collegeboard.com/student/testing/sat/prep_one/test.html
http://www.actstudent.org/testprep/
http://www.freesat1prep.com/
http://www.pinkmonkey.com/studyguides/subjects/sat/contents.asp
PSAT Info
Overview
PSAT stands for Preliminary SAT. It is good practice for the SAT, which contains the same types of questions. The PSAT tests critical reading, math problem solving, and writing skills.
http://education.yahoo.com/college/essentials/practice_tests/psat/
http://www.educationplanner.com/education_planner/preparing_article.asp?sponsor=2859&articleName=PSAT_Info
http://www.collegeboard.com/student/testing/psat/about.html
Good luck.
Kevin, Liverpool, England.