Depending on temperature, humidity and other conditions paint may take longer to dry than stated on the paint can. There are a few things you can do to make your paint dry faster.
The simple answer is to put a fan in the room to circulate the air. The increased air flow will help the paint dry faster. You can also accomplish this by opening one window in the room you have painted and another window in a different room. This should create a cross draft that will also help dry the paint.
There is not much you can do to make exterior paint dry faster. Typically latex paints will dry fast outside but oil-based paints can take up to 24 hours to become tack-free. Before painting with oil-based paint next time, try adding a product called Japan Drier. It will dramatically increase the dry time of oil-based paints.