La Femme Nikita - Boxed sets are in the $80 range though, but a really cool series. Vol 1-3 are out currently. Loosely based on the French movie, but a good adaptation as opposed to the horrible american movie remake.
Babylon 5 - Best SF series on TV ever IMHO. There are also boxed sets for the movies (most of which are less good) and Crusade which are in the $50 range. Crusade is best if you have watched B5, but is enjoyable in its own right. The episode with the Alien Porn was particularly amusing (Something you'd never see in STNG's "Perfect World"). As was the X-Files parody episode.
Dead Like Me - Very good, very funny episodes. Slacker Girl is killed by Toilet Seat from Mir Spacestation, finds out there is life after death, she's now a grim reaper and there is no free lunch after death so she still has to get a job. The main character does do a LOT of whining for the first 3 or 4 episodes, which I found difficult to sit through, but the rest of the series makes it worthwhile.
UFO : The classic Gerry Anderson SF series is out on DVD, but the boxed sets are very expensive $110 iirc. However, it is still a very good series. The clothing and designs are very '60s, especially for the "Far off Future of 1980!", but it has a unique feel and Cmdr. Straker is a ruthless hardcase like in no other series I've ever seen.
Black Adder : One of the funniest TV series of all time. Kind of expensive though $110 or so.
Red Dwarf : A bit of an acquired taste, but silll very funny.
Monarch of The Glen : Just pick up the two seasons, it goes downhill after that, but the first two are very entertaining.
The Vicar of Dhibbly : Great Series staring Dawn French as the first female Vicar in a small town full of odd characters.
Twin Peaks : Only Season one is out so far, but that was the best part anyway. One of the best series ever on TV.