Some of my picks:
Sapphire and Steel: No budget, but tons of creepy atmosphere and good chemistry between the two leads. Surprised no ones tried to remake it.
Lexx: thoroughly odd and starts to fall apart after the first two seasons, and also had no budget, but goofy fun.
Space 1999: odd mix of 2001 and Star Trek. Good stuff.
Tron: my local library does movie night and I took my kids to see it on the big screen. Cheesy, but we all enjoyed it.
Black Hole: This one gets a lot of grief, but I love it.
All the Trek franchises, except Enterprise.
Farscape: only ever saw the first season, but loved the characters. Have to see if netflix carries it.
almost any, cheesy 50's movie featuring a giant monster ( Them, 3 million miles to Earth, etc)
Battle Beyond the stars: The magnificent seven in space done on a budget of fifty bucks!
Well, I could go on all night, but that's a good start.