What to do with a 5 month old?

[Stillmonday]

Aside from baby massage classes and trips to the shops & visiting family & friends.. what else can I do with my 5 month old?
I find it hard to plan a full day out as he gets grumpy if he doesn't have his naps. What do people do?

I never have a full day out. We go swimming or to baby groups of the shops but I time all outings by naps - I will nap him in the car often if I can. He's a much happier baby if he gets proper naps.

My baby isn't much of a car napper so if I plan a day out he ends up really grumpy & unhappy.