Worcester Film Works shows a movie on the Common the third Thursday of June, July, and August.
West Boylston Cinema shows first- and second-run movies for far less than other cinemas. ($3.50 on Bargain Tuesdays!)
The Leicester Triple Drive-In costs $20 a carload for a double feature.
The Strand Theatre in Clinton is $5.50 for all shows/$5 for matinees.
The Elm Draught House Cinema in Millbury is $5 for all shows.
Cinema 320 at Clark University shows foreign/art house films for $6.00 adults, $4.00 seniors, $3.00 Clark students, faculty and staff.
The Seelos Theater at Holy Cross offers free movies during the school year.
The Mendon Drive-In is $25 a carload for a double feature.
Nicole, Worcester 
The Worcester Public Library shows free movies every Saturday afternoon, courtesy of the Friends of the Library. Each month has a theme, with a mix of older and more recent films. You can see the schedule of upcoming titles here:
http://wplreferenceblog.blogspot.com/search/label/Friends%20Film%20Series