Search the online catalog for books, DVDs, e-books, audio books, etc.
When searching use more general search terms than you would when searching a database of journal articles. For example, do a SUBJECT search on math to see the many subjects and entries listed under each.
When you find an item that looks useful, check the subject headings - you can click on them to see similar items. Also, it may be useful to click on the call number in the record. This allows you to virtually browse the titles as though you were standing in the stacks, except you'll also see any e-books in the collection.
Need some background information to help decide on a topic? Have you read an article and are confused on the lingo? Reference works, both print and online, will help you get started with your research. Here are some online reference databases you may find useful.