Stanford Encyclopedia of Philosophy - Great resource for getting the scoop on just about every philosophical issue and philosophers. All entries are peer-reviewed by professors of philosophy from around the world.
Internet Encyclopedia of Philosophy - Another great resource for getting the scoop on just about every philosophical issue and philosophers. All entries are peer-reviewed by professors of philosophy from around the world.
Routledge Encyclopedia of Philosophy - More philosophy!
Episteme Links - This site does what I'm trying to do here, but better.
PhilPapers - online database for papers in philosophy.
SparkNotes - just enter the book or paper you are trying to understand and SparkNotes will give you sufficient analyses.
Keith DeRose's page on Epistemology - Keith DeRose is a leading epistemologist at Yale. His page offers great insights into what top epistemologists are doing whether in writing or in their classes.
Google Scholar - it's like google but focused only on scholarly work. If you can't find a paper or a text anywhere, this site might remedy your situation.
The Philosophical Gourmet - If you are interested in pursuing a graduate degree in philosophy, this is one of the most comprehensive sources that provides students with breakdowns by university and specialty by department. Lots of additional informative content to help the unsuspecting prepare for the application process to a graduate school.
Understanding Necessary and Sufficient Conditions - Speaks for itself.