One idea is to check with any local museums around you. Many have one or two nights a month where it is free to get in. No museums close by? Check with local art galleries - it's free to browse!
Many libraries have free occasions where local authors and experts stop by, as well as showings of neat indie films. Check with your local library to see what's going on in your area!
Skip the dinner and go out for dessert and coffee instead. Or go out earlier in the evening when there are often half price appetizers and drinks during happy hour.
Really want the whole dinner experience on a monthly basis? Purchase your local Entertainment Book and get tons of coupons for buy one, get one free dining experiences. Even many small towns have coupon booklets for local restaurants and businesses for sale - check with your local Chamber of Commerce.
Have a favorite restaurant? Ask if they have a email list - I get coupons for several of our favorites on a regular basis just by having signed up for their emails.
How about date night at home? Blockbuster has movie rentals for $0.99 and $1.99, (membership is free) or get newer releases through a Redbox location for just $1 each night.