New Relativity
NewRelativity.net uses Einstein's Special Theory of Relativity to explore new paradoxes and thought experiments.  These articles present existing theoretical results in new ways and present new theory not found anywhere else.  The main topics are force and acceleration, including gravity.  In some ways, the Special Theory has advantages over Einstein's General Theory of Relativity in understanding the physics of acceleration, gravity and force.  The basis for these articles is college level Relativity theory (common established Relativity theory).  Each article is about 10 pages long.
The articles may be found here.
Some of the points of interest on this web site are:

1)   The way length contraction occurs during acceleration is explained
       (see the articles and discussion leading up to equation (38) in the
       article
Rocket Relativity)

2)   A demonstration of the Equivalence Principle is given, showing the conditions
      where clock readings, dimensions and forces are the same for dynamic and
      gravitational experiments    (see the articles
Special Relativity and
      Acceleration,Rocket Relativity, Energy Based Special Relativity, Special
     Relativity and Gravity
and Gravity and Mass)

3)   Formulas for the transformation of particle position, velocity and
      accelerations in two-dimensional motion are given  (see the article 
2 Dim.
      Position,Velocity, Acceleration
)

4)   A way that the geometry of an experiment can distort to produce the effects
      given by the equation of particle dynamics is shown   (see the article  
Force
       and Geometry
)

5)   An explanation is given as to why it is better to express relativity
      transformations as a function of energy differences between reference frames
      instead of as a function of velocity    (see the aricles   
Energy Based Special
      Relativity
and Special Relativity and Gravity)

6)   The reason that energy stored in gravitational fields has dynamic mass and
       gravitational mass (is attracted by other gravitational fields) is given   (see
       the discussion surrounding Figure 4 in the article
Special Relativity and
       Gravity
)

7)    Accelerations can appear and disappear in dynamic experiments, depending
       upon the motion of the observing reference frame   (see the articles 
Force
       and Geometry
, Force and Time and Energy Dynamics)

Many other interesting issues are also covered.
"Force" is the key idea here, where Einstein concentrated on "acceleration".  The study of force provides some clues as to how the physics of gravity and acceleration work, while Einstein's General Theory of Relativity shows what happens in a gravity field.  The Special Theory of Relativity is suited to this task, as the Special Theory is so much easier to use than the General Theory.  Each paradox or thought experiment presented is explained to confirm established principles of Relativity Theory.