The Times puts together a cute article about fan-created Trek.
The article, though, gets it a bit wrong about some of the motivations behind creating these bits of fandom; it suggests that the motivating factor is the recent cancellation of the late (and in some quarters, not-so-lamented) Enterprise and the subsequent lack of new, available Trek; this is, however, not really right, since many of the longer-running fan-based productions predate the demise of Enterprise; in fact, if memory serves, some of them actually have their genesis in the Voyager era. It seems to me that these fan-produced episodes are really much more of an extension of fan fiction, rather than a reaction to the lack of officially-sanctioned Trek.
As a side note, it must have been a really slow Saturday in the newsroom, because the article ran on the front page of the Sunday Times.
DO NOT MOCK MY MEME FOR IT IS JUST AND MEET.
Furthermore, the driving force behind most of the fan-created Trek shows is the desire to recreate the original series, a desire that was only intensified by the lack of continuities and other shortcomings of Enterprise. Also, the later era fan shows are simply embarrassing, whereas the ones they featured are much more interesting and professional.