I'm a big fan of enrichment outside the house. Both of my sons have been in weekly playgroups since they were infants, and it's been a HUGE lifesaver. We also do music class, library class (almost always free), field trips, etc. Since DS2 is now two, I'm also going to be co-teacihng an early preschool co-op for him in the fall.
As DH put it the other day, "Having gifted children takes a LOT of energy!" My kids really don't want to just play around the house for more than a few hours a day. They're social, and so am I. We tend to go somewhere mid-morning most days of the week, and then enjoy our afternoons at home (until DS1's schedule intervenes!). I try to have one or two "just at home" days, but they would much rather be out discovering things with other kids.
I also swear by joining a sports club. I don't go more than an hour a few times a week, but the boys love the playcenters and get lots of social interaction with different toys, art, etc., and I can work out in peace and quiet!
