Welcome to the club! The Libraries have a large number of science databases. The Web is full of others. How do you know where to go first? So much depends on what you are looking for. Amy and I did some workshops for the undergrad research students this summer and have developed several webpages to help them. Maybe they can help you too:
But here's a list I just ran across in Gary Price's Resource Shelf Newsletter that enumerates and annotates the "free" sources of science information on the web. No one place has it all. If you must be comprehensive, then you need to utilize all of the possible places where information is stored. Spending time doing this background research can save you lab time and maybe even lives.
A Quick Look of a Few Free Science Search Tools (Scirus, Live Search Academic, Google Scholar, Scitopia, Global Science Gateway, and More)