Another classic trek movie, this one from 1986, is awesome, and the most shocking thing about it is that it doesn't even take place in space, save for about 15 minutes! Instead it takes place in 1986, where the crew members go back in time to capture two whales to stop the destructive calls of an intergalactic whale species trying to contact the long-extinct whales. The whole plot sounds like it would suck beyond belief, but it comes close to being the best trek movie, and is one of my faves ever.
The awesomeness of the movie, unlike the rest of the series, comes not from suspense and action scenes, but the hilarious and often touching culture shock the crew faces in mid-80's San Fransisco. There is so much to laugh at: the crew earnestly walking along the SanFran streets, Sulu in his cape, Kirk in his red StarFleet uniform, and unforgettably, Spock in his monk robe with the belt tied around the tops of his pointy ears, making him look like an angry ninja master with a botched Botox job. Also hilarious is McCoy's disgust at how rudimentary 20th Century medical practices are/were. In a scene inside a hospital, he asks a woman what ails her, she responds she has kidney dialysis, and he's like, "What is this, the dark ages?! Swallow this, and call me if you have any problems." Several scenes later she is wheeled out claiming a miracle.
There is much more in the movie I won't spoil for you (or more like I'm too f*#&ing lazy to write any more), so turn the PC off and rent this great flick, also it's been on AMC recently, so try that too.