We went to everything our sure start centres had on offer, as much as I could fit in around naps! Creative classes, dancing, cooking, physical/active groups (like tumble tots), basically anything they had we went to.
I also found this age a great time to walk to the shops and to teach him how to be in a shop. I did it as an activity rather than trying to get the weekly shop done, so my focus was on him, how he walked around the shop, what he may or may not pick up, the need to stay close at the check out, helping carry basket/bag etc.
Trips to pet shop, DIY shops (homebase), car shops (halfords), electric goods (comet), train station, road works with barriers and diggers, basically any new experience.