There are a number of tools that can be used for studying the Gospel. The ones I find the most helpful are listed below:
Below is a short overview of the Gospel Topics section of the Church website.
Searchable collection of speeches delivered at Brigham Young University by Church leaders and others. Take a look at the quick intro to this great tool below:
Online access to the Encyclopedia of Mormonism. Here is a quick introduction to this excellent online tool:
Complete index of all scripture passages used in general conference talks.
All of the talks in different formats given from 1971 to the present.
Easy to browse text format.