My kids are older so it is much easier than when they were toddlers/babies.
Dh works evenings 4-midnight Mon to Fri. So, I can pretty easily leave the kiddos with him for things I don't want them around for (like pap smears like a previous poster LMAO! Or haircuts), or if I am a bit crabby and there is a high risk I might not be so patient with them like on a long grocery store trip. On Saturdays and Sundays dh will sometimes do the winding down for bed routine with them, so I can go have a bath or go out to a coffee shop myself. For working out, I have weights/kettlebells etc in my basement, and go and workout in the mornings before they get up generally. If they do come with me for things, we always pack a goodie bag like when they were toddlers...ds's Playmobile, sketchboard/markers for dd, picture search books, etc.
one thing we have found hard is home renovations. I have been sanding/wallprepping/painting for THREE freaking years now. My friends all laugh and ask what is taking so long, and I reply that it's not like my kids are out of the house for 6hrs a day in school!
Generally I try to take them though, as I think it is good for them to be in public learning social niceties like waiting in bank and grocery store lines! Just today I ran a few errands, and dd came with me; she chit chatted with some people in line about their babies, was thrilled to order the sushi we treated ourselves to, and made a purchase of a toy with her allowance. You know, real world stuff while the rest of kids her age are in school.