You can usually find what you want by doing a search. The WEB pages I have given below are just a few, which I have used.
Some sites have free downloadable software that is particularly useful in chemistry.
This is the site to download Adobe Acrobat Reader. This reads PDF file which are used for many files especially file with graphics. It will be very useful when you get to organic chemistry. It comes with a help file that you will want. This site also has Chime, a molecular modeling program.