By now, you've heard the great news: CBS is planning a new Star Trek television series in 2017. New Star Trek has not been present on television since the glorious conclusion to the franchise with the finale of Enterprise.*
There have been many spin-off and reboot attempts since the end of the original series in 1969. A few, such as The Next Generation, were successful. Others never made it to written scripts, let alone prepared pilot episodes.
Uproxx has described and ranked 5 failed attempts at new Star Trek shows, including my favorite: a Harry Mudd-focused show. Yes, Harry Mudd--the funny and fun-loving criminal who appeared in 2 episodes of the original series and 1 of the animated series. Gene Roddenberry once told Roger C. Carmel, the actor who played Mudd, that NBC wanted a Harry Mudd spin-off show:
A Harry Mudd spin-off series was, at one time, being considered. After TOS ended, there was a party at the studio. In Roger’s words, “Gene Roddenberry was there and we started talking and Gene said, ‘It’s a shame that series thing for you never worked out.’ I said, ‘what series thing?’ He said, ‘Oh, didn’t you know? Well, after the successful Harry Mudd episodes, NBC wanted to know if I would develop a spin-off series for you starring the Harry Mudd character. A space pirate, intergalactic con-man kind of thing.’ ‘My God Gene, I didn’t know anything about that. What happened?’ He said, ‘Well, the artists didn’t have enough time to develop it.’ And, of course, you couldn’t blame Gene; he didn’t want to let somebody take it off in a direction he didn’t approve of. Since he didn’t have the time to handle it all, the Mudd series project died. But it was a real blow to me because that was the first time I had heard of it. But what a great chance that would have been for me to star in my own spin-off series.”
You can read the rest of the Uproxx list here, including a 2004 reboot proposal by J. Michael Straczynski, the creator of Babylon 5. If there's one person who can definitely be trusted with the Star Trek legacy, it's Straczynski.
*Which I will argue to my dying day. Enterprise was an excellent show and final episode was perfect.