These days most people do not have spare time. If they do, taking a walk or watching TV are two simple ways to fill in the gaps. More inventive activities are available. The newspaper and this website's calender have interesting activities that you can get involved with. Some things have a cost to them, as there are underlying costs to putting on many activities. Others, like the Peninsula, have activities that are free.
My Son-in-law retired at the end of 2010. He is now enrolled for a class as a pharmacy tech. This is totally different than the job he retired from. He is enjoying and learning so much from this.
You can also visit local, state and national parks. Find out the history of the park and explore. A pet can help you out of the empty nest syndrome. You will be surprised at how much company they are. They have needs and you have to tend to them or they will let you know it! Going shopping on a lazy morning or afternoon is a break from boredom. Who knows, you might see someone in the store that you know. Doing crafts or taking lessons in something new can also break the summer blues. There are so many things that a person can do, and soon you find that you are way too busy and wonder why!