I too had to join this fine forum to add to this thread
Here is a short list of movies I enjoyed and think can be good places to get some ideas:
Blood Creek - A pre-WW2 nazi scientist moves in with an American family to conduct occult research. Fast forward to modern times, two brothers stumble upon the scientist and the original(unaged)family. Hilarity ensues.
Eagle Eye - supercomputer tries to control America "for our protection."
I, Robot - Eagle Eye with robots.
Wax Work 1 and 2 - Time travel and proto-dimensions.
Splice - deals with genetic manipulation and possible dangers of.
The Puppetmasters - Alien parasites invade Earth.
Repo The Genetic Opera - Mega-corp sells vital organs to the populous and repos them if the recipients can't pay. It is an opera and they sing everything. You are warned!
Virus - Alien program infects a Russian sea vessel, creates a body for itself and cobbles together minions from the ship and crew in an effort to cleanse the Earth of it's "human problem."
There are more, I just can't remember them at the moment.
BTW... Split Second is an awesome film!
*EDIT* two more
Brotherhood of the Wolf - GREAT suspense movie! A must see! It is in French with sub-titled english
The Crazies - Government cover-up of a lost plane carrying biological weaponry.
*EDIT* One-mo-agin!
The Unborn - Dybbuk (type of demon) tries to enter our world through a family prone to having twins.
Ghost Ship - Reaper of Souls lure greedy salvagers to an abandoned ship.
13 Ghosts - A ghost collector builds an infernal machine in his home. All he needs is a willing sacrifice to make it work.
Arachnaphobia - Super-tarantulas
Push - Free empaths vs. government empaths.
a couple shows from the syfy channel, School Spirits & Paranormal Witness - recountings of real life hauntings.