As Stargrrl mentioned check out Meetup.com which is an international website. Odds are even if you live in a small town there are various hobby and interest groups listed in your surrounding area. The minute you log onto the website it automatically adjust for your location. You also have the option of entering in your zip code with a distance radius of your choosing.
Meetup.com has just about everything you can imagine from wine tasting, yoga, meditation, horse back riding, book clubs, theatre goers, singles networks, writing, and on and on. Anything you have an interest in there is a group that meets at least once a month to share in that activity. Over time you'll develop friendships.
Another avenue is to sign up for a Continuing Education course. These are usually a one and done deal types of classes or workshops specializing in something of your interest along the "How to..." genre.
Sometimes it helps to be pro-active by simply saying "hello" to strangers in your age group and explained that you recently located and was curious to know if there were any places in the area that people typically congregate..etc Eventually you'll meet someone who can assist you.
You might also look through community newspapers in the area for any upcoming events or festivals that you feel would appeal to people in your age group. It may be worthwhile to check out the neighborhood bar/tavern, pool hall, or bowling alley on a Friday/Saturday night if it's a really small town.
If things are real slow you may have to plan on visiting a neighboring town that has a larger population during the weekends. There are lots of folks who live in suburban towns outside of major cities like LA, NYC, Chicago or wherever there is a decent size city with activities and they go to these cities for fun and excitement on weekends.