If both you and your date are athletic, setting up a date around a sport can be a wonderfully good time without costing much at all.
Tennis: grab a couple of rackets and balls and head to some local community tennis courts. If you have a high school near you, many have courts that aren't used on weekends.
Basketball: Grab a basketball and head to the local school to shoot come baskets. Whether it is a fun game of one-on-one or a shooting game like "H-O-R-S-E" you can have a great afternoon together.
Frisbee: Grab a Frisbee, head to the local park or open ground area and toss it around together.
Baseball / Catch: Grab a couple of mitts and a ball and head for some open ground area. Toss the ball around and enjoy each other's company. **This also can be adapted into a question game date. Every time you toss the ball you can ask a question and when the person receives it, they must answer and throw it back. This is a great way to get to know a date that you haven't been going out with for a long time.
Football: Just as with baseball, tossing a football back and forth can be great fun. To make it easier, you may want to use a soft Nerf type style. If throwing back and forth loses it's interest, you can also run football plays.
no matter what sport you decide to do, you can spend quality time together at minimal cost -- and get some exercise in, too.