in theatres: Slither
If you enjoyed Tremors or 8 Legged Freaks, then this is for you. A meteor crashes into a quiet N. Carolina town (shot in Vancouver, BC though) and attacking alien worms are unleashed on the town. Stars Elizabeth Banks and the always-excellent Michael Rooker. Directed by Troma vet James Gunn, this film is justified in earning its R rating.
http://www.slithermovie.net/

on DVD: Creep
It stars the red head from Ron Lola Run (Franka Potente). She plays a girl who wants to catch the last train one night in the London subway. While waiting, she falls asleep and wakes up long after the last train stopped at the station and now she's locked in for the night. I enjoyed it, nice work on such a tiny budget and from a first-time director too.
http://www.creepthemovie.com/