Stephen Hawking has been one of the leading theoretical researchers on the concept of black holes. In his essay, "Baby Universes, Children of Black Holes" Black Holes on the Internet), he describes the evaporation of black holes and investigates where the mass goes after it has been evaporated, and what state it is in (i.e. will the same number of the same type of particle emerge as went in?).

^M Black Holes by Ted Bunn A quick reference guide with commonly asked questions about black holes answered.

Black Holes and Beyond provides a general overview of how black holes form, how we know anything about them as well as why they are important.

Clicking on General Relativity provides a text on the theory of general relativity as well as a nice picture of the Einstein's original paper on the subject. Also included is a picture illustrating the process of embedding, in which space is warped by a larger object. A brief explanation of gravitational time dilation can be found here as well as information on the math behind Einstein's theories and gravitational waves.

Look here for a brief history of black holes which includes a link to an explanation of Schwarzschild singularity and its relation to black holes. A link to Observational evidence provides the viewer with several images of predictions for the collisions of black holes, etc. Theories for "How the cosmos began" allows an interesting view of a cosmic timeline showing events since the Big Bang. Also included I in the original text is information concerning gravitational waves, the Big Bang, and how gravitational waves are formed.

A Black Hole is Born provides detailed description on how black holes are formed as well as further information on the concepts of singularity as well as gravitational radiation and gravitational redshift. Also included is a discussion of white dwarfs.

Other work being done which concerns black holes:

Visualizing Black Hole Spacetime provides a series of images designed to help the viewer comprehend the concepts of space-time (good luck).

Colliding Black Holes and Rotating Black Holes provide images for the purpose of visualization.

Black Hole Studies to Verify Einstein's Theory uses studies of black holes and the gravitational waves created by the collisions of these black holes in an attempt to prove that Einstein's theory of general relativity is correct.

Three Dimensional Numerical Relativity: The Evolution of Black Holes leads to a PostScript document that can be downloaded which describes the development new code for modeling the creation and change in black holes.

In fact, there is a repository of papers on black holes in PostScript format at the NCSA General Relativity Group's page for papers on black holes.