You can probably find it in any video rental place. I've seen it at all the local ones near me so i'd say it's a safe bet you can find it.
Or you could take the leap and buy it used on DVD here. www.amazon.com/Salems-Lot-David-Soul/dp/0790742829/ref...1-1

But i should warn you that from what i hear it isn't too good so you may want to just try renting it before you buy. :)

Watch it on the 'Salem's Lot' spot here on fanpop (http://www.fanpop.com/spots/salems-lot). Word to the wise though, the film is kind of dated and isn't as good as the book.

Try looking in the Horror movies section of Fanpop
the one with the Michael Myers face.I think they have it posted under the videos section.

amazon.com is a great place to find stephen king movies. i even found the version of the shining where stephen king directed it on there at a super great price it only cost me $3