Hi, risendemon,
Variable speed of light theories are actually a very old idea; the VSL proposal of Joao Magueijo is only the most recent contender. Older versions ran into various problems, which are discussed in many review papers on problems in cosmology. Magueijo's proposal was received with considerable interest some years ago
http://arxiv.org/find/grp_physics/1/.../0/1/0/all/0/1
but I haven't been following its fortunes of late.
While searching unsuccessfully for a recent review paper for you, I found
http://www.answersingenesis.org/docs...cdk_davies.asp, from a "Creation Science" [sic] website which is apparently maintained by M. and T. Garoutte in KY. The Garouttes incorreclty claim "General Relativity has had a variable speed of light ever since 1917". This misstatement confuses
coordinate speeds with
velocities. VSL theories maintain that the
physical speed of light varies--- gtr is
not a VSL theory! The wider point here is: be careful of what you read on the internet. Not every page you find which claims to describe "science" would be recognized as such by scientists, and "Creation Science" [sic] websites are notoriously (sometimes hilariously) wrong about what gtr says (sometimes even what Galileo said!--- the website of Robert Sungenis
http://en.wikipedia.org/wiki/Robert_Sungenis claims, not just that Einstein was wrong, but even that Kepler was wrong!)