Bio/Chem/Materials Engineers (Heading back to Uni, any advice on your fields of study?)

After abandoning my English degree and traveling for a bit, I'm heading back to Uni next year, and am looking for some ways in which I can prepare myself ahead of time. Do you guys know of any online refresher resources that are easily accessible for Math/Bio/Chem? I've taken Trig, Calc, Alg, some 200 level Bio&Chem courses but it's been some years and feel I should start from the bottom on my own these next few months so I can hit the books hard when I return. (side note, I have no access to my old text books, as they are in an entirely different country.) Thanks guys for your time and I love what you all do here! I hope to be among the ranks one day.