I've been retired since June and I am taking two courses at an OLLI program (Osher lifelong Learning institute) at a local university that unlike a community college program the courses are tailored for the mostly retired 50+ age group. The first couple of classes have been engaging and mind stimulating and some members meet after class for lunch or dinner to discuss common interests. Not sure if there is a program near you.
I started going to OLLI classes as soon as I RE'd 3 yrs ago. I've also organized 4 science classes for our OLLI and that has given me the opportunity to interact with all the campus professors and students that I recruit as speakers. I serve on our OLLI curriculum committee and participate in the OLLI summer lunch meet ups. So that fills in most of my social needs.
I also have monthly dinners with a couple of college buddies. I also lunch with my former co-workers every couple of months. We've gotten to the point where they don't even talk about work that much.
I found a book club that I attend 4-5x per year. I found this club through meetups.com
For the past 15 yrs I've been salsa dancing 2-3x per week so that is another obvious social opportunity for me too.
During the day though, I mostly do things on my own. Today I rode my motorcycle into the city to try out a new lunch spot.