Your timing is great, because we're in the middle of a resurgence of sci fi model kits.
Round 2/Polar Lights has some great newer Star Trek kits, in addition to reissues of the old kits. If you want to start small and slow, their 1/1000 Enterprises (TOS and refit) are fantastic little 12" kits. If you're ambitious, they also make both kits in 1/350 scale at almost 3 feet long.
Moebius Models has been blessing us with big new kits of the vehicles from Lost in Space, Voyage to the Bottom of the Sea, and the New Galactica (among other properties!) for a few years now, with a Viper and Galactica from the old series planned for this year.
I recommend you check out the web stores at www.starshipmodeler.com
and shop, shop, shop.